Typescript loop through string with index and value

Question

I want to loop through a string and I want to have both the index and the character at this index. I know I could use a simple for loop for this, but I thought some of the newer features of Javascript/Typescript might be more elegant, so I tried this:

for (const [i, character] of Object.entries('Hello Stackoverflow')) {
    console.log(i);
    console.log(typeof(i));
    console.log(character);
}

Amazingly this works, however even though i counts up, it is a string. So for example this doesn't work:

'other string'.charAt(i)

I'm new at Typescript, so my questions are:

Why is i a string and not a number?
Is there a simpler / more elegant way to do this?

i is a number.

zerkms
– zerkms

2019-11-12 10:18:35 +00:00
Commented Nov 12, 2019 at 10:18 — zerkms
– zerkms, Commented Nov 12, 2019 at 10:18
i outputs '1' '2' and so on, and typeof(i) prints 'string'

Fels
– Fels

2019-11-12 10:21:50 +00:00
Commented Nov 12, 2019 at 10:21 — Fels
– Fels, Commented Nov 12, 2019 at 10:21
Yeah, my bad, didn't realise that.

zerkms
– zerkms

2019-11-12 10:27:25 +00:00
Commented Nov 12, 2019 at 10:27 — zerkms
– zerkms, Commented Nov 12, 2019 at 10:27

zerkms · Accepted Answer · 2019-11-12 10:24:52Z

29

The unicode-safe way would be to split to characters using spread syntax:

const chars = [...text];

Then you iterate using good old Array.prototype.forEach

chars.forEach((c, i) => console.log(c, i));

answered Nov 12, 2019 at 10:24

zerkms

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3 Comments

Vladtn Over a year ago

Looks elegant however I get this error for const chars = [...text];:

Type 'string' is not an array type or a string type. Use compiler option '--downlevelIteration' to allow iterating of iterators.ts(2569)

zerkms Over a year ago

"Type 'string' is not an array type or a string type" --- this looks awkward: what exactly your text is? @Vladtn

Vladtn Over a year ago

Changing target from es5 to es2015 or es6 fixes the issue, see stackoverflow.com/a/59662571/331719

user12251171 · Accepted Answer · 2019-11-12 10:19:24Z

10

Why is i a string and not a number?

Because Object.entries() returns a key-value pair and is intended to be used for objects, where keys are of course strings.

Is there a simpler / more elegant way to do this?

Just a simple for loop with charAt(i) can do the trick:

const text = 'Hello StackOverflow';
for (let i = 0; i < text.length; i++) {
  const character = text.charAt(i);
  console.log(i, character);
}

answered Nov 12, 2019 at 10:19

user12251171

3 Comments

zerkms Over a year ago

text.charAt could break unicode characters. Try with const text = '👨‍👩‍👧‍👦';

Fels Over a year ago

@bauke So what I would have done in plain Javascript anyway, thanks! :)

zerkms Over a year ago

@Fels it's broken though

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