Why Typescript can't use includes function for array?

Question

I know that Typescript use ES6 or ES2015.

And I know that anArray.includes('ifExist'); only available in ES6.

But why can't I use it when I use Typescript? It says that anArray don't have a method includes.

My Array

anArray = [
    {
        'category': 'x',
        'data': []
    }, 
    {
        'category': 'y',
        'data': []
    }, 
    {
        'category': 'z',
        'data': []
    }
];

ifExist variable

ifExist = {
    'category': 'a',
    'data': []
};

If I use anArray.indexOf(isExist) < 0, I can get the result like anArray.includes(isExist).

Your anArray is probably not typed as an array. You need to provide code that reproduces the problem — zerkms
– zerkms, Commented Sep 9, 2018 at 11:35

Pritilender · Accepted Answer · 2018-09-09 11:46:01Z

8

You need to specify target in your ts-config.json to ES2016 (or higher) in order to use Array.includes.

answered Sep 9, 2018 at 11:46

Pritilender

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4 Comments

Michael Harley Over a year ago

I see, it's my mistake too, includes method is in ES2016, not ES2015. And I use ES2015. I thought includes is in ES2015. Then this answer will definitely solve my problem. Thank you. :)

Ahmed Fasih Over a year ago

Is there a place where this information is kept? I was thinking maybe MDN would tell me which version of EcmaScript this was introduced but it doesn't seem to 😕

Pritilender Over a year ago

@AhmedFasih I mainly use node.green to check this, although its purpose is to list which ecmascript features are available in which node version.

Ahmed Fasih Over a year ago

Oh interesting! Yes I see it under "Node.js ES2016 Support"! Thank you!! I was grepping for another function in this directory: github.com/microsoft/TypeScript/tree/main/src/lib 😅 this is much better

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