2.14 pluck

2.14.1 语法:

_.pluck(list, key)

2.14.2 说明:

pluck方法根据key对list数组中的每个对象进行检索,返回检索成功的属性值,否则返回undefined,返回一个数组

  • list为数组和arguments(数组中需要是对象类似:{x: 1})
  • key是一个字符串

2.14.3 代码示例:

示例一:根据key来检索数组对象

var result;

// 操作数组对象
result = _.pluck([{name: 'moe', age: 30}, {name: 'curly', age: 50}], 'name');
console.log(result); //=> ["moe", "curly"] //操作arguments
function abc() {
result = _.pluck([{name: 'moe', age: 30}, {name: 'curly', age: 50}], 'name');
console.log(result); //=> ["1.0", "2.0", "3.0"]
}
abc({name: 'moe', age: 30}, {name: 'curly', age: 50});

2.14.4 检索不到对应的key

var result = _.pluck([{ name: 'moe', age: 30 }, { name: 'curly', age: 50 }], 'sex');
console.log(result); //=> [undefined, undefined]

2.14.5 常见误区:

var result;

// list为字符串
result = _.pluck('ab', 'sex');
console.log(result); //=> [undefined, undefined] // list为对象
result = _.pluck({ x: 1, y: 2 }, 'sex');
console.log(result); //=> [undefined, undefined]

2.14.5 特殊情况:

var result;

result = _.pluck([{ '[object Object]': 1 }, { x: 2 }], {});
console.log(result); //=> [1, undefined] // list为null、true、undefined等等则返回一个空数组
result = _.pluck(null, 'sex');
console.log(result); //=> []
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