Translate ES6 'for' loop from ES5 'for-each' loop

Question

I need help with translating the following es6 loop to es5 code.

for (let [field_name, field] of impList) {
//// some code
}

Thanks.

That depends a lot on what impList is. A Map? An array?

Bergi
– Bergi

2016-06-02 14:37:25 +00:00
Commented Jun 2, 2016 at 14:37 — Bergi
– Bergi, Commented Jun 2, 2016 at 14:37
Have you tried using a transpiler? Use Babel.

Bergi
– Bergi

2016-06-02 14:38:39 +00:00
Commented Jun 2, 2016 at 14:38 — Bergi
– Bergi, Commented Jun 2, 2016 at 14:38

CodingIntrigue · Accepted Answer · 2016-06-02 14:29:31Z

8

Assuming that impList is an Array (or an array-like object), and not an ES6 Iterable type (which would require polyfills, etc), you can roughly translate that to a for loop:

for (var i=0; i<impList.length; i++) {
    var field_name = impList[i][0];
    var field = impList[i][1];
}

Or a forEach:

impList.forEach(function(entry) {
    var field_name = entry[0];
    var field = entry[1];
});

In addition to impList possibly being an Iterable, there are some nuances here that I didn't translate to ES5, because there are quite a lot of caveats. Which is why you should be using a transpiler such as Babel.

edited Jun 2, 2016 at 14:29

answered Jun 2, 2016 at 14:07

CodingIntrigue

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4 Comments

badigard Over a year ago

to be honest, I dont understand Babel's code: for (var _iterator = impList.entries()[Symbol.iterator](), _step; !(_iteratorNormalCompletion = (_step = _iterator.next()).done); _iteratorNormalCompletion = true) { var _step$value = _slicedToArray(_step.value, 2); var field_name = _step$value[0]; var _field = _step$value[1]; }

CodingIntrigue Over a year ago

Babel's output is written for computers, not humans :) It includes polyfills, shims & functionality to address the nuances I described above. All you need to know is you put in ES6 and it outputs valid ES5!

badigard Over a year ago

When I put the es5 code, I get error on 'Symbol' object.

badigard Over a year ago

My project is in ES5. I am refactoring ES6 to ES5. Do I need to include it to write ES5?

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