angular-cn/packages/common/upgrade/src/utils.ts

/**
 * @license
 * Copyright Google LLC All Rights Reserved.
 *
 * Use of this source code is governed by an MIT-style license that can be
 * found in the LICENSE file at https://angular.io/license
 */

export function stripPrefix(val: string, prefix: string): string {
  return val.startsWith(prefix) ? val.substring(prefix.length) : val;
}

export function deepEqual(a: any, b: any): boolean {
  if (a === b) {
    return true;
  } else if (!a || !b) {
    return false;
  } else {
    try {
      if ((a.prototype !== b.prototype) || (Array.isArray(a) && Array.isArray(b))) {
        return false;
      }
      return JSON.stringify(a) === JSON.stringify(b);
    } catch (e) {
      return false;
    }
  }
}

export function isAnchor(el: (Node&ParentNode)|Element|null): el is HTMLAnchorElement {
  return (<HTMLAnchorElement>el).href !== undefined;
}

export function isPromise<T = any>(obj: any): obj is Promise<T> {
  // allow any Promise/A+ compliant thenable.
  // It's up to the caller to ensure that obj.then conforms to the spec
  return !!obj && typeof obj.then === 'function';
}