#prefer-string-starts-ends-with

#Configuration

import { defineConfig, ts } from '@rslint/core';

export default defineConfig([
  ts.configs.recommended,
  {
    rules: {
      '@typescript-eslint/prefer-string-starts-ends-with': 'error',
    },
  },
]);

#Rule Details

Enforce using String#startsWith and String#endsWith over other equivalent methods of checking substrings.

There are multiple ways to verify if a string starts or ends with a specific string, such as foo.indexOf('bar') === 0, foo.charAt(0) === 'b', or regex tests like /^bar/.test(foo). Since ES2015 has added String#startsWith and String#endsWith, this rule reports on other ways of checking, suggesting the use of the built-in methods instead.

Examples of incorrect code for this rule:

declare const foo: string;

foo[0] === 'b';
foo.charAt(0) === 'b';
foo.indexOf('bar') === 0;
foo.slice(0, 3) === 'bar';
foo.substring(0, 3) === 'bar';
foo.match(/^bar/) != null;
/^bar/.test(foo);

foo[foo.length - 1] === 'b';
foo.charAt(foo.length - 1) === 'b';
foo.lastIndexOf('bar') === foo.length - 3;
foo.slice(-3) === 'bar';
foo.substring(foo.length - 3) === 'bar';
foo.match(/bar$/) != null;
/bar$/.test(foo);

Examples of correct code for this rule:

declare const foo: string;

foo.startsWith('bar');
foo.endsWith('bar');

foo.startsWith('a');
foo.endsWith('a');

#Options

#allowSingleElementEquality

When set to "always", allows equality checks for a single character (e.g. foo[0] === 'a' and foo.charAt(0) === 'a').

{
  "@typescript-eslint/prefer-string-starts-ends-with": [
    "warn",
    { "allowSingleElementEquality": "always" }
  ]
}

#Original Documentation

• typescript-eslint prefer-string-starts-ends-with