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Implement for...of iterator via Symbol.iterator #1197

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May 14, 2018
Merged

Implement for...of iterator via Symbol.iterator #1197

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d8aaef5
Implement for...of iterator via Symbol.iterator
papandreou May 12, 2018
4f27a2d
Merge branch 'v1.0.0' into feature/iteratorSymbol
fb55 May 13, 2018
c6bdc79
Assert that the iterator ends
papandreou May 13, 2018
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6 changes: 6 additions & 0 deletions lib/cheerio.js
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Original file line number Diff line number Diff line change
@@ -1,3 +1,4 @@
/*global Symbol*/
/*
Module dependencies
*/
Expand Down Expand Up @@ -138,6 +139,11 @@ Cheerio.prototype.toArray = function() {
return this.get();
};

// Support for (const element of $(...)) iteration:
if (typeof Symbol !== 'undefined') {
Cheerio.prototype[Symbol.iterator] = Array.prototype[Symbol.iterator];
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This will fit better in api/traversing.js

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@papandreou papandreou May 13, 2018 •
edited
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That was what I tried first (so it could live near each), but it didn't work because the export of api/traversing.js is being mixed into Cheerio.prototype using _.extend, which does not include Symbol keys:

const mySymbol = Symbol('foo');
const a = { [mySymbol]: 123 };

console.log(a[mySymbol]); // 123
const b = require('lodash').extend({}, a);
console.log(b[mySymbol]); // undefined

Fixing that would involve iterating over Object.getOwnPropertySymbols(mod) as well, and that seemed way too invasive.

}

// Plug in the API
api.forEach(function(mod) {
_.extend(Cheerio.prototype, mod);
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16 changes: 16 additions & 0 deletions test/api/traversing.js
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Original file line number Diff line number Diff line change
@@ -1,3 +1,4 @@
/*global Symbol*/
var expect = require('expect.js'),
cheerio = require('../..'),
food = require('../fixtures').food,
Expand Down Expand Up @@ -680,6 +681,21 @@ describe('$(...)', function() {
});
});

if (typeof Symbol !== 'undefined') {
describe('[Symbol.iterator]', function() {

it('should yield each element', function() {
// The equivalent of: for (const element of $('li')) ...
var $li = $('li'),
iterator = $li[Symbol.iterator]();
expect(iterator.next().value.attribs['class']).to.equal('apple');
expect(iterator.next().value.attribs['class']).to.equal('orange');
expect(iterator.next().value.attribs['class']).to.equal('pear');
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Can you also assert that iteration terminates as expected?

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@papandreou papandreou May 13, 2018 •
edited
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Absolutely, fixed in c6bdc79

expect(iterator.next().done).to.equal(true);
});
});
}

describe('.map', function() {
it('(fn) : should be invoked with the correct arguments and context', function() {
var $fruits = $('li');
Expand Down