javascript parsing int values into int

Question

I have an array of objects and there is the property id which may contains integers or strings. I'm using that property to compare, but now I'm guessing if it is more efficient to always convert that id in integer even if it is an integer or to ask if it is an string and then convert it. I mean this:

let myArray = [{id: 1, ...otherprops}, {id: 2, ...otherprops}, {id: '3', ...otherprops}, {id: '4', ...otherprops}];

Is this more efficient ...

for (let x of myArray) {
   if (parseInt(x.id, 10) === 3) {
      ...
   }
}

Or this code:

for (let x of myArray) {
   let id = -1;
   if (typeof x.id === 'string') {
      id = parseInt(x.id, 10);
   }
   if (id === 3) { ... }
}

Since the first code always convert I don't know if two conditions are better.

@Bian Goole -- the parsing tag is not about conversion of strings to numeric types; please read about the intended uses of tags before adding them.... — ad absurdum
– ad absurdum, Commented Oct 19, 2017 at 13:19
@DavidBowling I appreciate your comment, it was the way I found to a quick solution. I reading now what you've suggested. — assembler
– assembler, Commented Oct 19, 2017 at 13:22

Nina Scholz · Accepted Answer · 2017-10-19 13:15:04Z

3

If you know, that you have just numbers or stringed numbers, then you could take an unary plus + for conversion to a number, which does not change numbers.

var id = +x.id;

answered Oct 19, 2017 at 13:15

Nina Scholz

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1 Comment

assembler Over a year ago

that's it, it solves the problem... I didn't know that... thanks

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