StringChecks.ts

// Copyright (c) Microsoft Corporation. All rights reserved. Licensed under the MIT license.
// See LICENSE in the project root for license information.

import * as ts from 'typescript';

/**
 * Helpers for validating various text string formats.
 */
export class StringChecks {
  /**
   * Tests whether the input string is safe to use as an ECMAScript identifier without quotes.
   *
   * @remarks
   * For example:
   *
   * ```ts
   * class X {
    *   public okay: number = 1;
    *   public "not okay!": number = 2;
    * }
    * ```
    *
    * A precise check is extremely complicated and highly dependent on the ECMAScript standard version
    * and how faithfully the interpreter implements it.  To keep things simple, `isSafeUnquotedMemberIdentifier()`
    * conservatively accepts any identifier that would be valid with ECMAScript 5, and returns false otherwise.
    */
   public static isSafeUnquotedMemberIdentifier(identifier: string): boolean {
    if (identifier.length === 0) {
      return false; // cannot be empty
    }

    if (!ts.isIdentifierStart(identifier.charCodeAt(0), ts.ScriptTarget.ES5)) {
      return false;
    }

    for (let i: number = 1; i < identifier.length; i++) {
      if (!ts.isIdentifierPart(identifier.charCodeAt(i), ts.ScriptTarget.ES5)) {
        return false;
      }
    }

    return true;
  }
}