simple array question

Question

I have a 2 dimension array :

var fondetcaption = [
        ["fond/fond1.jpg","« aaa"],    
        ["fond/fond2.jpg","« bbb"],
        ["fond/fond3.jpg","« ccc"],
        ["fond/fond4.jpg","« ddd"]          
    ];

That array can have 4, 7, 10, any number of value in...

I like to know how many pair of value I have (it should return 4 in this case)

var howmany = fondetcaption.lenght; // doesn't work !

And after that... i will show fondetcaption[0][0] (the first background) and after that on click on a button i like to show the next : [1][0] and then next [2][0] and then [3][0] and then [0][0] again.... push doesn't seem to work.

Any idea?

Answer 1

As the others have said, it's length, not lenght.

But no one seems to have addressed the second part of your question, so:

You don't need push to cycle through the values. All you need is an index:

var fondetcaption = [
    ["fond/fond1.jpg","« aaa"],    
    ["fond/fond2.jpg","« bbb"],
    ["fond/fond3.jpg","« ccc"],
    ["fond/fond4.jpg","« ddd"]          
];
var fondetcaptionIndex = 0;

// Call this when you click your button or whatever
function getNextBackground() {
    if (fondetcaptionIndex >= fondetcaption.length) {
        fondetcaptionIndex = 0;
    }
    return fondetcaption[fondetcaptionIndex++];
}

Or, if you like, you can just put the index directly on the array object, since JavaScript array objects can have arbitrary non-element properties and that helps keep the symbols together:

var fondetcaption = [
    ["fond/fond1.jpg","« aaa"],    
    ["fond/fond2.jpg","« bbb"],
    ["fond/fond3.jpg","« ccc"],
    ["fond/fond4.jpg","« ddd"]          
];
fondetcaption.index = 0;

// Call this when you click your button or whatever
function getNextBackground() {
    if (fondetcaption.index >= fondetcaption.length) {
        fondetcaption.index = 0;
    }
    return fondetcaption[fondetcaption.index++];
}

In fact, you can even make the function part of the array:

var fondetcaption = [
    ["fond/fond1.jpg","« aaa"],    
    ["fond/fond2.jpg","« bbb"],
    ["fond/fond3.jpg","« ccc"],
    ["fond/fond4.jpg","« ddd"]          
];
fondetcaption.index = 0;
fondetcaption.getNext = function() {
    if (this.index >= this.length) {
        this.index = 0;
    }
    return this[this.index++];
};

// Use
background = fondetcaption.getNext();

If making the array itself the container of those extra properties bothers you (it bothers some people), wrap the whole thing up in an object:

var fondetcaption = (function() {
    var index = 0,
        values = [
            ["fond/fond1.jpg","« aaa"],    
            ["fond/fond2.jpg","« bbb"],
            ["fond/fond3.jpg","« ccc"],
            ["fond/fond4.jpg","« ddd"]          
        ];

    function fondetcaption_getNext() {
        if (index >= values.length) {
            index = 0;
        }
        return values[index++];
    }

    return {
        values:  values,
        getNext: fondetcaption_getNext
    };
})();

// Sample use:
background = fondetcaption.getNext();

// Original array still accessible if desired as fondetcaption.values

Answer 2

check your spelling..

fondetcaption.length

Answer 3

Did you try:

var howmany = fondetcaption.length;

Your original post has a spelling error, lenght needs to be length.

Answer 4

Try length.

alert(fondetcaption.length);

Answer 5

Not sure what's wrong since it works fine here..

var fondetcaption = [
        ["fond/fond1.jpg","« aaa"],    
        ["fond/fond2.jpg","« bbb"],
        ["fond/fond3.jpg","« ccc"],
        ["fond/fond4.jpg","« ddd"]          
];

alert(fondetcaption.length); 

http://jsfiddle.net/tLPwp/

Perhaps fondetcaption.lenght is actually copied from code, and thusly spelled incorrectly.

Answer 6

This returns the array's length: fondetcaption.length

Answer 7

You have a typo in code. It should be var howmany = fondetcaption.length, and not ... fondetcaption.lenght.

I suggest you use tools like Firebug's, Chrome's, or Safari's Console. It can be very helpful, especially with the problems like these. I copy-pasted your code, tried it, and it works like charm. With the mentioned typo fixed, of course.

Cheers.