Why does using `this` within function give me a "Possible strict violation" in jshint?

Question

Say I have a function that I would like reuse as a method on a couple objects in order to add data to those objects.

function addToObject(data) {
  for (var d in data) {
    if (data.hasOwnProperty(d)) {
      this[d] = data[d];
    }
  }
}

myObjOne = {
  add: addToObject
};

myObjTwo = {
  add: addToObject
};

My goal here was to be able to call myObjOne.add(myData) where myData is an object that I would like to add to myObjOne and be able to replicate this functionality on myObjTwo.

My issue is that using this within addToObject gives me:

this[d] = data[d];
^ Possible strict violation.

in jshint.

Why is this?

Answer 1

The docs say the warning happens when:

you use this in a non-constructor function. If you forget to use the new keyword when calling a constructor function, this will be bound unexpectedly to the global object in non-strict mode, but will be undefined in strict mode.

Use validethis:true in a pragma comment:

function addToObject(data) {
    'use strict';
    var d;
    for (d in data) {
        if (data.hasOwnProperty(d)) {
            /* jshint: validthis:true */
            this[d] = data[d];
        }
    }
}

References

• JsHint Options: validthis
• The Strict Mode Restriction and Exceptions