有一个版本的JavaScript的串。个()允许经常表达?
-
07-07-2019 - |
题
在javascript,是否有同等的串。个()就需要一个经常的表达,而不是一串的第一个第一个参数,同时仍然允许一个第二个参数?
我需要做些什么喜欢
str.indexOf(/[abc]/ , i);
和
str.lastIndexOf(/[abc]/ , i);
虽然串。搜索()需要regexp作为一个参数,它不允许我指定第二个说法!
编辑:
事实证明,这会比我原来是这么认为我写了一个小的功能测试,以测试所有提供解决方案...它假定regexIndexOf和regexLastIndexOf已经加入串的对象。
function test (str) {
var i = str.length +2;
while (i--) {
if (str.indexOf('a',i) != str.regexIndexOf(/a/,i))
alert (['failed regexIndexOf ' , str,i , str.indexOf('a',i) , str.regexIndexOf(/a/,i)]) ;
if (str.lastIndexOf('a',i) != str.regexLastIndexOf(/a/,i) )
alert (['failed regexLastIndexOf ' , str,i,str.lastIndexOf('a',i) , str.regexLastIndexOf(/a/,i)]) ;
}
}
和我的测试如下,以确保至少有一个字表示式,结果是一样的,如果我们使用的个
//寻找一中的修正
测试("xxx");
测试('axx');
测试('xax');
测试('xxa');
测试('axa');
测试('xaa');
测试('杂');
测试("aaa");
解决方案
结合已经提到的一些方法(indexOf显然相当简单),我认为这些功能可以解决这个问题:
String.prototype.regexIndexOf = function(regex, startpos) {
var indexOf = this.substring(startpos || 0).search(regex);
return (indexOf >= 0) ? (indexOf + (startpos || 0)) : indexOf;
}
String.prototype.regexLastIndexOf = function(regex, startpos) {
regex = (regex.global) ? regex : new RegExp(regex.source, "g" + (regex.ignoreCase ? "i" : "") + (regex.multiLine ? "m" : ""));
if(typeof (startpos) == "undefined") {
startpos = this.length;
} else if(startpos < 0) {
startpos = 0;
}
var stringToWorkWith = this.substring(0, startpos + 1);
var lastIndexOf = -1;
var nextStop = 0;
while((result = regex.exec(stringToWorkWith)) != null) {
lastIndexOf = result.index;
regex.lastIndex = ++nextStop;
}
return lastIndexOf;
}
显然,修改内置String对象会为大多数人发送红色标记,但这可能是一次没有那么大的交易;只是意识到它。
更新:编辑 regexLastIndexOf()
,以便现在似乎模仿 lastIndexOf()
。如果它仍然失败并且在什么情况下,请告诉我。
更新:通过本页评论中找到的所有测试,以及我自己的测试。当然,这并不意味着它是防弹的。任何反馈意见。
其他提示
String
构造函数的实例有 .search()
方法,它接受一个RegExp并返回第一个匹配的索引。
要从特定位置开始搜索(伪造 .indexOf()
的第二个参数),您可以 slice
关闭第一个 i
字符:
str.slice(i).search(/re/)
但是这将使得索引在较短的字符串中(在第一部分被切掉之后),所以你需要将截断的部分( i
)的长度添加到返回的索引,如果它不是 -1
。这将为您提供原始字符串中的索引:
function regexIndexOf(text, re, i) {
var indexInSuffix = text.slice(i).search(re);
return indexInSuffix < 0 ? indexInSuffix : indexInSuffix + i;
}
我有一个简短的版本。它适用于我!
var match = str.match(/[abc]/gi);
var firstIndex = str.indexOf(match[0]);
var lastIndex = str.lastIndexOf(match[match.length-1]);
如果你想要一个原型版本:
String.prototype.indexOfRegex = function(regex){
var match = this.match(regex);
return match ? this.indexOf(match[0]) : -1;
}
String.prototype.lastIndexOfRegex = function(regex){
var match = this.match(regex);
return match ? this.lastIndexOf(match[match.length-1]) : -1;
}
编辑:如果您想添加对fromIndex的支持
String.prototype.indexOfRegex = function(regex, fromIndex){
var str = fromIndex ? this.substring(fromIndex) : this;
var match = str.match(regex);
return match ? str.indexOf(match[0]) + fromIndex : -1;
}
String.prototype.lastIndexOfRegex = function(regex, fromIndex){
var str = fromIndex ? this.substring(0, fromIndex) : this;
var match = str.match(regex);
return match ? str.lastIndexOf(match[match.length-1]) : -1;
}
要使用它,就像这样简单:
var firstIndex = str.indexOfRegex(/[abc]/gi);
var lastIndex = str.lastIndexOfRegex(/[abc]/gi);
您可以使用substr。
str.substr(i).match(/[abc]/);
基于BaileyP的回答。主要区别在于,如果模式无法匹配,这些方法将返回 -1
。
编辑:感谢Jason Bunting的回答,我有了一个主意。为什么不修改正则表达式的 .lastIndex
属性?虽然这只适用于带有全局标志的模式( / g
)。
修改:已更新以通过测试用例。
String.prototype.regexIndexOf = function(re, startPos) {
startPos = startPos || 0;
if (!re.global) {
var flags = "g" + (re.multiline?"m":"") + (re.ignoreCase?"i":"");
re = new RegExp(re.source, flags);
}
re.lastIndex = startPos;
var match = re.exec(this);
if (match) return match.index;
else return -1;
}
String.prototype.regexLastIndexOf = function(re, startPos) {
startPos = startPos === undefined ? this.length : startPos;
if (!re.global) {
var flags = "g" + (re.multiline?"m":"") + (re.ignoreCase?"i":"");
re = new RegExp(re.source, flags);
}
var lastSuccess = -1;
for (var pos = 0; pos <= startPos; pos++) {
re.lastIndex = pos;
var match = re.exec(this);
if (!match) break;
pos = match.index;
if (pos <= startPos) lastSuccess = pos;
}
return lastSuccess;
}
它本身并不存在,但您当然可以添加此功能
<script type="text/javascript">
String.prototype.regexIndexOf = function( pattern, startIndex )
{
startIndex = startIndex || 0;
var searchResult = this.substr( startIndex ).search( pattern );
return ( -1 === searchResult ) ? -1 : searchResult + startIndex;
}
String.prototype.regexLastIndexOf = function( pattern, startIndex )
{
startIndex = startIndex === undefined ? this.length : startIndex;
var searchResult = this.substr( 0, startIndex ).reverse().regexIndexOf( pattern, 0 );
return ( -1 === searchResult ) ? -1 : this.length - ++searchResult;
}
String.prototype.reverse = function()
{
return this.split('').reverse().join('');
}
// Indexes 0123456789
var str = 'caabbccdda';
alert( [
str.regexIndexOf( /[cd]/, 4 )
, str.regexLastIndexOf( /[cd]/, 4 )
, str.regexIndexOf( /[yz]/, 4 )
, str.regexLastIndexOf( /[yz]/, 4 )
, str.lastIndexOf( 'd', 4 )
, str.regexLastIndexOf( /d/, 4 )
, str.lastIndexOf( 'd' )
, str.regexLastIndexOf( /d/ )
]
);
</script>
我没有完全测试这些方法,但它们似乎到目前为止都有效。
RexExp
实例有 lastIndex 属性已经(如果它们是全局的)所以我正在做的是复制正则表达式,稍微修改它以适应我们的目的, exec
- 在字符串上查看它并查看<代码> lastIndex的代码>。这将不可避免地比在字符串上循环更快。 (你有足够的例子说明如何将它放到字符串原型上,对吗?)
function reIndexOf(reIn, str, startIndex) {
var re = new RegExp(reIn.source, 'g' + (reIn.ignoreCase ? 'i' : '') + (reIn.multiLine ? 'm' : ''));
re.lastIndex = startIndex || 0;
var res = re.exec(str);
if(!res) return -1;
return re.lastIndex - res[0].length;
};
function reLastIndexOf(reIn, str, startIndex) {
var src = /\$/.test(reIn.source) && !/\\\$/.test(reIn.source) ? reIn.source : reIn.source + '(?![\\S\\s]*' + reIn.source + ')';
var re = new RegExp(src, 'g' + (reIn.ignoreCase ? 'i' : '') + (reIn.multiLine ? 'm' : ''));
re.lastIndex = startIndex || 0;
var res = re.exec(str);
if(!res) return -1;
return re.lastIndex - res[0].length;
};
reIndexOf(/[abc]/, "tommy can eat"); // Returns 6
reIndexOf(/[abc]/, "tommy can eat", 8); // Returns 11
reLastIndexOf(/[abc]/, "tommy can eat"); // Returns 11
您还可以将函数原型化到RegExp对象上:
RegExp.prototype.indexOf = function(str, startIndex) {
var re = new RegExp(this.source, 'g' + (this.ignoreCase ? 'i' : '') + (this.multiLine ? 'm' : ''));
re.lastIndex = startIndex || 0;
var res = re.exec(str);
if(!res) return -1;
return re.lastIndex - res[0].length;
};
RegExp.prototype.lastIndexOf = function(str, startIndex) {
var src = /\$/.test(this.source) && !/\\\$/.test(this.source) ? this.source : this.source + '(?![\\S\\s]*' + this.source + ')';
var re = new RegExp(src, 'g' + (this.ignoreCase ? 'i' : '') + (this.multiLine ? 'm' : ''));
re.lastIndex = startIndex || 0;
var res = re.exec(str);
if(!res) return -1;
return re.lastIndex - res[0].length;
};
/[abc]/.indexOf("tommy can eat"); // Returns 6
/[abc]/.indexOf("tommy can eat", 8); // Returns 11
/[abc]/.lastIndexOf("tommy can eat"); // Returns 11
快速解释我如何修改 RegExp
:对于 indexOf
,我只需要确保设置了全局标志。对于 lastIndexOf
,我使用负面预测来查找最后一次出现,除非 RegExp
已经在字符串的末尾匹配。
让所有提议的解决方案以某种方式失败我的测试后,(编辑:一些在我写完之后更新以通过测试)我找到了 Array.indexOf 和 Array.lastIndexOf
我使用它们来实现我的String.prototype.regexIndexOf和String.prototype.regexLastIndexOf版本,如下所示:
String.prototype.regexIndexOf = function(elt /*, from*/)
{
var arr = this.split('');
var len = arr.length;
var from = Number(arguments[1]) || 0;
from = (from < 0) ? Math.ceil(from) : Math.floor(from);
if (from < 0)
from += len;
for (; from < len; from++) {
if (from in arr && elt.exec(arr[from]) )
return from;
}
return -1;
};
String.prototype.regexLastIndexOf = function(elt /*, from*/)
{
var arr = this.split('');
var len = arr.length;
var from = Number(arguments[1]);
if (isNaN(from)) {
from = len - 1;
} else {
from = (from < 0) ? Math.ceil(from) : Math.floor(from);
if (from < 0)
from += len;
else if (from >= len)
from = len - 1;
}
for (; from > -1; from--) {
if (from in arr && elt.exec(arr[from]) )
return from;
}
return -1;
};
他们似乎通过了我在问题中提供的测试功能。
显然,只有当正则表达式匹配一个字符时它们才有效,但这对我的目的来说已经足够了,因为我将它用于诸如([abc],\ s,\ W,\ D)之类的东西
我会继续监控这个问题,以防有人提供更好/更快/更清洁/更通用的实现,适用于任何正则表达式。
我还需要一个 regexIndexOf
函数用于数组,所以我自己编写了一个。但我怀疑,它已经过优化,但我想它应该可以正常工作。
Array.prototype.regexIndexOf = function (regex, startpos = 0) {
len = this.length;
for(x = startpos; x < len; x++){
if(typeof this[x] != 'undefined' && (''+this[x]).match(regex)){
return x;
}
}
return -1;
}
arr = [];
arr.push(null);
arr.push(NaN);
arr[3] = 7;
arr.push('asdf');
arr.push('qwer');
arr.push(9);
arr.push('...');
console.log(arr);
arr.regexIndexOf(/\d/, 4);
在某些简单的情况下,您可以使用拆分来简化向后搜索。
function regexlast(string,re){
var tokens=string.split(re);
return (tokens.length>1)?(string.length-tokens[tokens.length-1].length):null;
}
这有一些严重的问题:
- 重叠匹配不会显示
- 返回的索引是匹配结束而不是开始(如果你的正则表达式是一个常数,则很好) 醇>
但从好的方面来看,代码更少。对于不能重叠的恒定长度正则表达式(如 / \ s \ w /
来查找字边界),这已经足够了。
对于具有稀疏匹配的数据,使用string.search是浏览器中最快的。它会在每次迭代时将字符串重新切片为:
function lastIndexOfSearch(string, regex, index) {
if(index === 0 || index)
string = string.slice(0, Math.max(0,index));
var idx;
var offset = -1;
while ((idx = string.search(regex)) !== -1) {
offset += idx + 1;
string = string.slice(idx + 1);
}
return offset;
}
对于密集数据,我做了这个。与execute方法相比,它更复杂,但对于密集数据,它比我尝试的其他方法快2-10倍,比接受的解决方案快约100倍。要点是:
- 它会在传入的正则表达式上调用exec以验证是否匹配或提前退出。我这样做是使用(?=在类似的方法中,但在使用exec进行IE检查时要快得多。
- 它以'(r)。(?!。?r)' 的格式构造和缓存修改后的正则表达式
-
执行新的正则表达式并返回exec或第一个exec的结果;
function lastIndexOfGroupSimple(string, regex, index) { if (index === 0 || index) string = string.slice(0, Math.max(0, index + 1)); regex.lastIndex = 0; var lastRegex, index flags = 'g' + (regex.multiline ? 'm' : '') + (regex.ignoreCase ? 'i' : ''), key = regex.source + '
醇>
我不了解测试的目的。需要正则表达式的情况无法与对indexOf的调用进行比较,我认为这是首先制定该方法的重点。为了让测试通过,使用'xxx +(?!x)'比调整正则表达式迭代的方式更有意义。
+ flags, match = regex.exec(string); if (!match) return -1; if (lastIndexOfGroupSimple.cache === undefined) lastIndexOfGroupSimple.cache = {}; lastRegex = lastIndexOfGroupSimple.cache[key]; if (!lastRegex) lastIndexOfGroupSimple.cache[key] = lastRegex = new RegExp('.*(' + regex.source + ')(?!.*?' + regex.source + ')', flags); index = match.index; lastRegex.lastIndex = match.index; return (match = lastRegex.exec(string)) ? lastRegex.lastIndex - match[1].length : index; }; 醇>我不了解测试的目的。需要正则表达式的情况无法与对indexOf的调用进行比较,我认为这是首先制定该方法的重点。为了让测试通过,使用'xxx +(?!x)'比调整正则表达式迭代的方式更有意义。
Jason Bunting的最后一个指数不起作用。我的不是最优的,但它确实有效。
//Jason Bunting's
String.prototype.regexIndexOf = function(regex, startpos) {
var indexOf = this.substring(startpos || 0).search(regex);
return (indexOf >= 0) ? (indexOf + (startpos || 0)) : indexOf;
}
String.prototype.regexLastIndexOf = function(regex, startpos) {
var lastIndex = -1;
var index = this.regexIndexOf( regex );
startpos = startpos === undefined ? this.length : startpos;
while ( index >= 0 && index < startpos )
{
lastIndex = index;
index = this.regexIndexOf( regex, index + 1 );
}
return lastIndex;
}
还有没有本地的方法执行请求的任务。
这里是代码,我在使用。它模仿的行为 String.原型。个 和 String.原型。lastIndexOf 方法,但他们也接受一个RegExp作为搜索参数以外的一串代表的价值进行搜索。
是的它是相当长作为一个答案顺利,因为它试图按照目前的标准,尽可能接近和当然包含合理数量的 JSDOC 评论意见。然而,一旦缩小,代码是只有2.27k和一次压缩,用于传送这只是1023字节。
对2的方法,这增加了 String.prototype
(使用 对象。defineProperty 如适用):
searchOf
searchLastOf
它通过所有测试的运算公布,此外我已经测试的程序相当彻底的在我的日常使用情况,并试图确保他们的工作跨越多个环境,但是,反馈意见/问题都总是受欢迎的。
/*jslint maxlen:80, browser:true */
/*
* Properties used by searchOf and searchLastOf implementation.
*/
/*property
MAX_SAFE_INTEGER, abs, add, apply, call, configurable, defineProperty,
enumerable, exec, floor, global, hasOwnProperty, ignoreCase, index,
lastIndex, lastIndexOf, length, max, min, multiline, pow, prototype,
remove, replace, searchLastOf, searchOf, source, toString, value, writable
*/
/*
* Properties used in the testing of searchOf and searchLastOf implimentation.
*/
/*property
appendChild, createTextNode, getElementById, indexOf, lastIndexOf, length,
searchLastOf, searchOf, unshift
*/
(function () {
'use strict';
var MAX_SAFE_INTEGER = Number.MAX_SAFE_INTEGER || Math.pow(2, 53) - 1,
getNativeFlags = new RegExp('\\/([a-z]*)$', 'i'),
clipDups = new RegExp('([\\s\\S])(?=[\\s\\S]*\\1)', 'g'),
pToString = Object.prototype.toString,
pHasOwn = Object.prototype.hasOwnProperty,
stringTagRegExp;
/**
* Defines a new property directly on an object, or modifies an existing
* property on an object, and returns the object.
*
* @private
* @function
* @param {Object} object
* @param {string} property
* @param {Object} descriptor
* @returns {Object}
* @see https://goo.gl/CZnEqg
*/
function $defineProperty(object, property, descriptor) {
if (Object.defineProperty) {
Object.defineProperty(object, property, descriptor);
} else {
object[property] = descriptor.value;
}
return object;
}
/**
* Returns true if the operands are strictly equal with no type conversion.
*
* @private
* @function
* @param {*} a
* @param {*} b
* @returns {boolean}
* @see http://www.ecma-international.org/ecma-262/5.1/#sec-11.9.4
*/
function $strictEqual(a, b) {
return a === b;
}
/**
* Returns true if the operand inputArg is undefined.
*
* @private
* @function
* @param {*} inputArg
* @returns {boolean}
*/
function $isUndefined(inputArg) {
return $strictEqual(typeof inputArg, 'undefined');
}
/**
* Provides a string representation of the supplied object in the form
* "[object type]", where type is the object type.
*
* @private
* @function
* @param {*} inputArg The object for which a class string represntation
* is required.
* @returns {string} A string value of the form "[object type]".
* @see http://www.ecma-international.org/ecma-262/5.1/#sec-15.2.4.2
*/
function $toStringTag(inputArg) {
var val;
if (inputArg === null) {
val = '[object Null]';
} else if ($isUndefined(inputArg)) {
val = '[object Undefined]';
} else {
val = pToString.call(inputArg);
}
return val;
}
/**
* The string tag representation of a RegExp object.
*
* @private
* @type {string}
*/
stringTagRegExp = $toStringTag(getNativeFlags);
/**
* Returns true if the operand inputArg is a RegExp.
*
* @private
* @function
* @param {*} inputArg
* @returns {boolean}
*/
function $isRegExp(inputArg) {
return $toStringTag(inputArg) === stringTagRegExp &&
pHasOwn.call(inputArg, 'ignoreCase') &&
typeof inputArg.ignoreCase === 'boolean' &&
pHasOwn.call(inputArg, 'global') &&
typeof inputArg.global === 'boolean' &&
pHasOwn.call(inputArg, 'multiline') &&
typeof inputArg.multiline === 'boolean' &&
pHasOwn.call(inputArg, 'source') &&
typeof inputArg.source === 'string';
}
/**
* The abstract operation throws an error if its argument is a value that
* cannot be converted to an Object, otherwise returns the argument.
*
* @private
* @function
* @param {*} inputArg The object to be tested.
* @throws {TypeError} If inputArg is null or undefined.
* @returns {*} The inputArg if coercible.
* @see https://goo.gl/5GcmVq
*/
function $requireObjectCoercible(inputArg) {
var errStr;
if (inputArg === null || $isUndefined(inputArg)) {
errStr = 'Cannot convert argument to object: ' + inputArg;
throw new TypeError(errStr);
}
return inputArg;
}
/**
* The abstract operation converts its argument to a value of type string
*
* @private
* @function
* @param {*} inputArg
* @returns {string}
* @see https://people.mozilla.org/~jorendorff/es6-draft.html#sec-tostring
*/
function $toString(inputArg) {
var type,
val;
if (inputArg === null) {
val = 'null';
} else {
type = typeof inputArg;
if (type === 'string') {
val = inputArg;
} else if (type === 'undefined') {
val = type;
} else {
if (type === 'symbol') {
throw new TypeError('Cannot convert symbol to string');
}
val = String(inputArg);
}
}
return val;
}
/**
* Returns a string only if the arguments is coercible otherwise throws an
* error.
*
* @private
* @function
* @param {*} inputArg
* @throws {TypeError} If inputArg is null or undefined.
* @returns {string}
*/
function $onlyCoercibleToString(inputArg) {
return $toString($requireObjectCoercible(inputArg));
}
/**
* The function evaluates the passed value and converts it to an integer.
*
* @private
* @function
* @param {*} inputArg The object to be converted to an integer.
* @returns {number} If the target value is NaN, null or undefined, 0 is
* returned. If the target value is false, 0 is returned
* and if true, 1 is returned.
* @see http://www.ecma-international.org/ecma-262/5.1/#sec-9.4
*/
function $toInteger(inputArg) {
var number = +inputArg,
val = 0;
if ($strictEqual(number, number)) {
if (!number || number === Infinity || number === -Infinity) {
val = number;
} else {
val = (number > 0 || -1) * Math.floor(Math.abs(number));
}
}
return val;
}
/**
* Copies a regex object. Allows adding and removing native flags while
* copying the regex.
*
* @private
* @function
* @param {RegExp} regex Regex to copy.
* @param {Object} [options] Allows specifying native flags to add or
* remove while copying the regex.
* @returns {RegExp} Copy of the provided regex, possibly with modified
* flags.
*/
function $copyRegExp(regex, options) {
var flags,
opts,
rx;
if (options !== null && typeof options === 'object') {
opts = options;
} else {
opts = {};
}
// Get native flags in use
flags = getNativeFlags.exec($toString(regex))[1];
flags = $onlyCoercibleToString(flags);
if (opts.add) {
flags += opts.add;
flags = flags.replace(clipDups, '');
}
if (opts.remove) {
// Would need to escape `options.remove` if this was public
rx = new RegExp('[' + opts.remove + ']+', 'g');
flags = flags.replace(rx, '');
}
return new RegExp(regex.source, flags);
}
/**
* The abstract operation ToLength converts its argument to an integer
* suitable for use as the length of an array-like object.
*
* @private
* @function
* @param {*} inputArg The object to be converted to a length.
* @returns {number} If len <= +0 then +0 else if len is +INFINITY then
* 2^53-1 else min(len, 2^53-1).
* @see https://people.mozilla.org/~jorendorff/es6-draft.html#sec-tolength
*/
function $toLength(inputArg) {
return Math.min(Math.max($toInteger(inputArg), 0), MAX_SAFE_INTEGER);
}
/**
* Copies a regex object so that it is suitable for use with searchOf and
* searchLastOf methods.
*
* @private
* @function
* @param {RegExp} regex Regex to copy.
* @returns {RegExp}
*/
function $toSearchRegExp(regex) {
return $copyRegExp(regex, {
add: 'g',
remove: 'y'
});
}
/**
* Returns true if the operand inputArg is a member of one of the types
* Undefined, Null, Boolean, Number, Symbol, or String.
*
* @private
* @function
* @param {*} inputArg
* @returns {boolean}
* @see https://goo.gl/W68ywJ
* @see https://goo.gl/ev7881
*/
function $isPrimitive(inputArg) {
var type = typeof inputArg;
return type === 'undefined' ||
inputArg === null ||
type === 'boolean' ||
type === 'string' ||
type === 'number' ||
type === 'symbol';
}
/**
* The abstract operation converts its argument to a value of type Object
* but fixes some environment bugs.
*
* @private
* @function
* @param {*} inputArg The argument to be converted to an object.
* @throws {TypeError} If inputArg is not coercible to an object.
* @returns {Object} Value of inputArg as type Object.
* @see http://www.ecma-international.org/ecma-262/5.1/#sec-9.9
*/
function $toObject(inputArg) {
var object;
if ($isPrimitive($requireObjectCoercible(inputArg))) {
object = Object(inputArg);
} else {
object = inputArg;
}
return object;
}
/**
* Converts a single argument that is an array-like object or list (eg.
* arguments, NodeList, DOMTokenList (used by classList), NamedNodeMap
* (used by attributes property)) into a new Array() and returns it.
* This is a partial implementation of the ES6 Array.from
*
* @private
* @function
* @param {Object} arrayLike
* @returns {Array}
*/
function $toArray(arrayLike) {
var object = $toObject(arrayLike),
length = $toLength(object.length),
array = [],
index = 0;
array.length = length;
while (index < length) {
array[index] = object[index];
index += 1;
}
return array;
}
if (!String.prototype.searchOf) {
/**
* This method returns the index within the calling String object of
* the first occurrence of the specified value, starting the search at
* fromIndex. Returns -1 if the value is not found.
*
* @function
* @this {string}
* @param {RegExp|string} regex A regular expression object or a String.
* Anything else is implicitly converted to
* a String.
* @param {Number} [fromIndex] The location within the calling string
* to start the search from. It can be any
* integer. The default value is 0. If
* fromIndex < 0 the entire string is
* searched (same as passing 0). If
* fromIndex >= str.length, the method will
* return -1 unless searchValue is an empty
* string in which case str.length is
* returned.
* @returns {Number} If successful, returns the index of the first
* match of the regular expression inside the
* string. Otherwise, it returns -1.
*/
$defineProperty(String.prototype, 'searchOf', {
enumerable: false,
configurable: true,
writable: true,
value: function (regex) {
var str = $onlyCoercibleToString(this),
args = $toArray(arguments),
result = -1,
fromIndex,
match,
rx;
if (!$isRegExp(regex)) {
return String.prototype.indexOf.apply(str, args);
}
if ($toLength(args.length) > 1) {
fromIndex = +args[1];
if (fromIndex < 0) {
fromIndex = 0;
}
} else {
fromIndex = 0;
}
if (fromIndex >= $toLength(str.length)) {
return result;
}
rx = $toSearchRegExp(regex);
rx.lastIndex = fromIndex;
match = rx.exec(str);
if (match) {
result = +match.index;
}
return result;
}
});
}
if (!String.prototype.searchLastOf) {
/**
* This method returns the index within the calling String object of
* the last occurrence of the specified value, or -1 if not found.
* The calling string is searched backward, starting at fromIndex.
*
* @function
* @this {string}
* @param {RegExp|string} regex A regular expression object or a String.
* Anything else is implicitly converted to
* a String.
* @param {Number} [fromIndex] Optional. The location within the
* calling string to start the search at,
* indexed from left to right. It can be
* any integer. The default value is
* str.length. If it is negative, it is
* treated as 0. If fromIndex > str.length,
* fromIndex is treated as str.length.
* @returns {Number} If successful, returns the index of the first
* match of the regular expression inside the
* string. Otherwise, it returns -1.
*/
$defineProperty(String.prototype, 'searchLastOf', {
enumerable: false,
configurable: true,
writable: true,
value: function (regex) {
var str = $onlyCoercibleToString(this),
args = $toArray(arguments),
result = -1,
fromIndex,
length,
match,
pos,
rx;
if (!$isRegExp(regex)) {
return String.prototype.lastIndexOf.apply(str, args);
}
length = $toLength(str.length);
if (!$strictEqual(args[1], args[1])) {
fromIndex = length;
} else {
if ($toLength(args.length) > 1) {
fromIndex = $toInteger(args[1]);
} else {
fromIndex = length - 1;
}
}
if (fromIndex >= 0) {
fromIndex = Math.min(fromIndex, length - 1);
} else {
fromIndex = length - Math.abs(fromIndex);
}
pos = 0;
rx = $toSearchRegExp(regex);
while (pos <= fromIndex) {
rx.lastIndex = pos;
match = rx.exec(str);
if (!match) {
break;
}
pos = +match.index;
if (pos <= fromIndex) {
result = pos;
}
pos += 1;
}
return result;
}
});
}
}());
(function () {
'use strict';
/*
* testing as follow to make sure that at least for one character regexp,
* the result is the same as if we used indexOf
*/
var pre = document.getElementById('out');
function log(result) {
pre.appendChild(document.createTextNode(result + '\n'));
}
function test(str) {
var i = str.length + 2,
r,
a,
b;
while (i) {
a = str.indexOf('a', i);
b = str.searchOf(/a/, i);
r = ['Failed', 'searchOf', str, i, a, b];
if (a === b) {
r[0] = 'Passed';
}
log(r);
a = str.lastIndexOf('a', i);
b = str.searchLastOf(/a/, i);
r = ['Failed', 'searchLastOf', str, i, a, b];
if (a === b) {
r[0] = 'Passed';
}
log(r);
i -= 1;
}
}
/*
* Look for the a among the xes
*/
test('xxx');
test('axx');
test('xax');
test('xxa');
test('axa');
test('xaa');
test('aax');
test('aaa');
}());
<pre id="out"></pre>
如果您正在寻找一个使用RegExp的非常简单的lastIndex查找,并且不关心它是否将lastIndexOf模仿到最后一个细节,这可能引起您的注意。
我只是反转字符串,并从长度中减去第一个出现的索引 - 1.它碰巧通过了我的测试,但我认为长字符串可能会出现性能问题。
interface String {
reverse(): string;
lastIndex(regex: RegExp): number;
}
String.prototype.reverse = function(this: string) {
return this.split("")
.reverse()
.join("");
};
String.prototype.lastIndex = function(this: string, regex: RegExp) {
const exec = regex.exec(this.reverse());
return exec === null ? -1 : this.length - 1 - exec.index;
};
好吧,因为你只是想匹配字符的位置,正则表达式可能有点过分。
我认为你想要的只是“而不是找到这些角色中的第一个”。 ,找到这些人物中的第一个。
这当然是一个简单的答案,但你的问题确实要做什么,虽然没有正则表达式部分(因为你没有澄清为什么特别是它必须是一个正则表达式)
function mIndexOf( str , chars, offset )
{
var first = -1;
for( var i = 0; i < chars.length; i++ )
{
var p = str.indexOf( chars[i] , offset );
if( p < first || first === -1 )
{
first = p;
}
}
return first;
}
String.prototype.mIndexOf = function( chars, offset )
{
return mIndexOf( this, chars, offset ); # I'm really averse to monkey patching.
};
mIndexOf( "hello world", ['a','o','w'], 0 );
>> 4
mIndexOf( "hello world", ['a'], 0 );
>> -1
mIndexOf( "hello world", ['a','o','w'], 4 );
>> 4
mIndexOf( "hello world", ['a','o','w'], 5 );
>> 6
mIndexOf( "hello world", ['a','o','w'], 7 );
>> -1
mIndexOf( "hello world", ['a','o','w','d'], 7 );
>> 10
mIndexOf( "hello world", ['a','o','w','d'], 10 );
>> 10
mIndexOf( "hello world", ['a','o','w','d'], 11 );
>> -1