Question

184

Passing scope to forEach

rated 0 times [ 190] [ 6] / answers: 1 / hits: 60295 / 11 Years ago, fri, november 1, 2013, 12:00:00

I'm trying to use a callback method addToCount instead of anonymous function in forEach. But I can't access this.count in it (returns undefined).

function Words(sentence) {

  this.sentence = sentence;

  this.count = {};

  this.countWords();

}



Words.prototype = {

  countWords: function() {

    var words = this.sentence.split(/W+/);

    words.forEach(this.addToCount);

  },

  addToCount: function(word) {

    word = word.toLowerCase();

    if (word == '') return;

    if (word in this.count)

      this.count[word] += 1;

    else

      this.count[word] = 1;

  }

}

I think the problem is the scope. How can I pass this to addToCount or is there any other way to make it work?

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darleneh

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2 Years ago

answered 11 Years ago calicinthias · Accepted Answer

You need to use Function#bind to bind a scope:

words.forEach(this.addToCount.bind(this));

Note that this is not available in all browsers: you should use a shim (as provided in the link above) to add it in the browsers that don't support Function#bind.

As dandavis points out in the comments, you can pass a value to Array#forEach as the context for the callback:

words.forEach(this.addToCount, this);