TypeScript A computed property name in a type literal must directly refer to a built-in symbol

Question

ERROR in...component.ts (..,..): A computed property name in a type literal must directly refer to a built- in symbol. ...: Cannot find name 'any'.

I'm looking forward an object which contains strings which have other string, ie:

{ abc: 'xyz' }

What I did:

foo: { [string]: string };

Answer 1

计算值上的识别名称是必需的：

foo: { [bar: string]: string };

Answer 2

I had a similar issue after building. The two issues I faced were with using numbers and or enum values as keys in objects. Just to help those that see this in the future.

Enums as keys

export enum MyEnum {
  one = 'stringOne',
  two = 'stringTwo',
}

export const someMap = {
  [ MyEnum.one ]: 'valueOne',
  [ MyEnum.two ]: 'valueTwo',
};

This will transpile someMap to a type that look something like...

export declare const someMap: {
  [ MyEnum.one ]: string;
  [ MyEnum.two ]: string;
};

Note the keys are still the enum value and not strings, typescript/angular does not like that because it is expecting something like...

export declare const someMap: {
  [ x: string ]: string;
};

So two possible fixes are...

1) Assign explicit type to someMap

export interface ForceStringType {
  [product: string]: string;
}
export const someMap: ForceStringType = {
  [ MyEnum.one ]: 'valueOne',
  [ MyEnum.two ]: 'valueTwo',
};

2) Assign string type to keys of someMap

export const someMap: ForceStringType = {
  [ MyEnum.one as string ]: 'valueOne',
  [ MyEnum.two as string ]: 'valueTwo',
};

Numbers as keys

const CONSTANT_ONE = 123;
const CONSTANT_TWO = 321;

export const someMap = {
  [ CONSTANT_ONE ]: 'valueOne',
  [ CONSTANT_TWO ]: 'valueTwo',
};

This will transpile someMap to a type that look something like...

export declare const someMap: {
  [ CONSTANT_ONE ]: string;
  [ CONSTANT_TWO ]: string;
};

Note the keys are still the constant/number value and not strings, typescript/angular is again expecting something like...

export declare const someMap: {
  [ x: string ]: string;
};

So one possible fix is...

Interpolate number as string for each key of someMap

export declare const someMap: {
  [ `${CONSTANT_ONE}` ]: string;
  [ `${CONSTANT_TWO}` ]: string;
};

Note: Accessing a value from someMap with the constant/number as a key should not matter as typescript will coerce it to a string anyway, but probably best for overall consistency.

 const valueOne: string = someMap[ CONSTANT_ONE ]; // vs const valueOne: string = someMap[ `${CONSTANT_ONE}` ];

Answer 3

The currently accepted answer will not work if the key type comes from a generic. For that to work, you need to use the in operator:

type WithKey<K extends string | number | symbol> = {
    [k in K]: boolean
}

Credit here .

Answer 4

I was having this issue in a Vue component, my problem was that I was incorrectly binding class names:

Vue documentation

<script lang="ts">
import { defineComponent } from '@vue/composition-api'

export default defineComponent({
  props: {
    className: String,
  },

  setup() {
    const isModified = computed<boolean>(() => true)

    return {
      isModified,
    }

<template>
  <!-- BAD -->
  <div 
    class="static-class" 
    :class="{ [className]: true, 'static-class--modified': isModified }]">
  </div>

  <!-- GOOD -->
  <div 
    class="static-class" 
    :class="[className, { 'static-class--modified': isModified }]">
  </div>
</template>