What should I use instead of a "for" loop when appending a number?

Question

I have heard that the for(){...} loop in JavaScript is passé and should not be used in favor of other, clearer alternatives. JSLint goes so far as to throw an error when it encounters one (unless you override it, of course). I understand using Array.prototype.forEach() when the situation allows, but in this instance what alternative could I use that would be "clearer"?

var number = 5;
for (var i=0; i <= number; i++){ 
    log("somestring" + i);
}

In C# I would use a foreach(){...} over Enumerable.Range(0, 5) - but I know of no such alternative in JavaScript. I could create an array of digits 0...5 but that seems like going the long way for no gain.

Edit 1

I am not looking for an alternative plugin to implement this like lodash or jQuery, and my question really isn't about "why does JSLint...". What native JavaScript alternative would I use?

Have you considered lodash ? It includes the range function you are looking for https://lodash.com/docs/4.17.4#range — klugjo, Dec 05 '17 at 04:27
JSLint throws an error because your loop only iterate once (because of the `return` statement) thus it is useless. Your whole code is the same as: `return "somestring" + 0;`. — ibrahim mahrir, Dec 05 '17 at 04:27
pass two parameters into the callback, the 2nd is the index. `arr.forEach(function(item, i){ console.log(item, i); });` — itodd, Dec 05 '17 at 04:28
Array Methods... look into them. https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array — epascarello, Dec 05 '17 at 04:35
Javascript does have a yield (return) - perhaps a better candidate for your example. https://stackoverflow.com/a/20859859/314291 — StuartLC, Dec 05 '17 at 04:37

A.D. · Answer 1 · 2017-12-05T04:38:55.950

return is not a good idea in between a loop in javascript.this overridden due to the same you can use break or continue instead to break the execution in between. There also to get the data as foreach jquery also allowed object map to the same as follows. and get the value for each as a dynamic string you can work as per the function is given below.

var number = 5;
var toReturn = function(){
var ar_data = []; 
for (var i=0; i <= number; i++){ 
    ar_data[i] = "somestring" + i;  // Store your dynamic string into a variable
}
return ar_data; // return array 
}
var data = toReturn(number);

for(dt in data) // foreach type object mapping and tracing 
{
console.log(data[dt]); //print the individual item in array.
}

Jaye Renzo Montejo · Accepted Answer · 2017-12-05T05:15:10.453

0

If you're using an array to store your numbers, use .reduce():

const num = [1, 2, 3, 4, 5]
const val = num.reduce((acc, curr) => `${acc}${curr}`, 'somestring')
console.log(val)

Edit: The thing is, if you don't want to use an array then the for loop would be the most readable. My advice is to just ignore what JSLint says.

I'll just post another suggestion. It uses the array indexes to generate an array:

[...Array(5).keys()].reduce((acc, curr) => `${acc}${curr + 1}`, 'somestring')

edited Dec 05 '17 at 05:15

answered Dec 05 '17 at 04:34

Jaye Renzo Montejo

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" I could create an array of digits 0...5 but that seems like going the long way for no gain." – Scott Baker Dec 05 '17 at 04:37
Reducing or folding strings causes the string concatenation problem. – StuartLC Dec 05 '17 at 04:38

What should I use instead of a "for" loop when appending a number?

2 Answers2