TS2339: Property 'includes' does not exist on type 'string'

Question

I have seen this error mentioned in regards to string arrays but not actual strings. I have a TypeScript file with the line

if (!bus.lineInfo.PublishedLineName.includes(input)) {

This gives me an error of

TS2339: Property 'includes' does not exist on type 'string'.

bus is a variable that implements the bus interface:

interface bus {
    "lineInfo": {
        "PublishedLineName": string,
        "DestinationName": string, // The headsign of the bus
        "Color": string,
        "TextColor": boolean | string // false if this is "FFFFFF", otherwise it's the color
    },
    "warnings": boolean | busWarnings
    "marker"?: google.maps.Marker,
    "result"?: JQuery // The search result that appears in the sidebar
}

lineInfo.PublishedLineName is declared as a string, and String.prototype.includes() is a function according to MDN, so why does the TypeScript compiler complain about the missing property/method?

I believe it is a string method; I've updated my post to reflect that along with a link — Michael Kolber, Aug 12 '18 at 17:36
What are the "target" and "lib" settings in your `tsconfig.json`? `String.includes` is in ES6. — Matt McCutchen, Aug 12 '18 at 17:49
@MattMcCutchen "target" is set to `es5`. I don't have a "lib" option set. Setting "lib" to "es2015" removes the string error but causes a bunch of errors in thea jQuery d.ts file I have from DefinitelyTyped. — Michael Kolber, Aug 12 '18 at 17:54

score 46 · Accepted Answer · answered Aug 12 '18 at 17:53

46

You should add es2016 or es7 lib complierOptions in tsconfig.json. Default TypeScript doesn't support some es6 polyfill functions

{
  "compilerOptions": {
    ...
    "lib": [
       "dom",
       "es7"
    ]
  }
}

Or change build target to es2016 if you no longer want to support ES5 anymore

{
  "compilerOptions": {
    ...
    "target" "es2016"
  }
}

answered Aug 12 '18 at 17:53

hgiasac

2,183
16
14

1

Perfect! Can you please explain what "dom" does/includes support for? – Michael Kolber Aug 12 '18 at 18:44
2

`dom` support frontend interface (DOM, Event...). Some library is used for both frontend and backend, when compiling it will alert syntax error. If you develop backend, and there is no error when compiling, you can remove it – hgiasac Aug 13 '18 at 02:31
9

This does not work in VSCode with Typescript 3.2.2. Has something changed in the last few months? – Lars Nyström Jan 07 '19 at 13:59
1

I'm facing same problem. Have you found anything in this regard @LarsNyström – Tushar Shukla Feb 16 '19 at 11:41
No, I was in over my head so I decided to stay away from TS for now. – Lars Nyström Feb 17 '19 at 12:50
I have the same problem – LiHao Dec 04 '20 at 11:19

score 3 · Answer 2 · answered Jun 15 '20 at 06:15

3

Add es2016.array.include to compilerOptions.lib

answered Jun 15 '20 at 06:15

Dimitar Nestorov

2,411
24
29

TS2339: Property 'includes' does not exist on type 'string'

2 Answers2

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