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一、数组相关

1、数值类型转数组

• JS版本

  const castArray = (value) => (Array.isArray(value) ? value : [value]);
  castArray(1); // [1]
  

• TS版本

  const castArray = <T,_>(value: T | T[]): T[] => (Array.isArray(value) ? value : [value]);
  castArray(1); // [1]
  

2、校验数组是否为空

• JS版本

  const isEmpty = (arr) => Array.isArray(arr) && !arr.length;
  isEmpty([]); // true
  

• TS版本

  const isEmpty = <T,_>(arr: T[]): boolean => Array.isArray(arr) && !arr.length;
  isEmpty([1, 2, 3]); // false
  

3、将对象数组转为单个对象

• JS版本

  const toObject = (arr, key) => arr.reduce((a, b) => ({ ...a, [b[key]]: b }), {});
    //Or
  const toObject = (arr, key) => Object.fromEntries(arr.map((it) => [it[key], it]));
  

• TS版本

  const toObject = <T extends Record<string, any>, K extends keyof T>(arr: T[], key: K): Record<string, T> => (
      arr.reduce((a, b) => ({ ...a, [b[key]]: b }), {})
  );
  // Or
  const toObject = <T extends Record<string, any>, K extends keyof T>(arr: T[], key: K): Record<string, T> => (
      Object.fromEntries(arr.map((it) => [it[key], it]))
  );
  

• 示例

   toObject(
      [
          { id: '1', name: 'Alpha', gender: 'Male' },
          { id: '2', name: 'Bravo', gender: 'Male' },
          { id: '3', name: 'Charlie', gender: 'Female' },
      ],
      'id'
  );
  /* 
  {
    '1': { id: '1', name: 'Alpha', gender: 'Male' },
    '2': { id: '2', name: 'Bravo', gender: 'Male' },
    '3': { id: '3', name: 'Charlie', gender: 'Female' },
  }
  */
  

4、两个数组比较

• JS版本

  // `a` and `b` are arrays
  const isEqual = (a, b) => JSON.stringify(a) === JSON.stringify(b);
  //Or
  const isEqual = (a, b) => a.length === b.length && a.every((v, i) => v === b[i]);
  isEqual([1, 2, 3], [1, 2, 3]); // true
  

• TS版本

  const isEqual = <T,_>(a: T[], b: T[]): boolean => JSON.stringify(a) === JSON.stringify(b);
  //Or
  const isEqual = <T,_>(a: T[], b: T[]): boolean => a.length === b.length && a.every((v, i) => v === b[i]);
  isEqual([1, 2, 3], [1, '2', 3]); // false