• _.reject：根据条件去除某个元素。

        var foo = [
        {id: 0, name: "aaa", age: 33},
        {id: 1, name: "bbb", age: 25}
        ]
        var bar = _.reject(foo, ['id', 0])
        //bar = [{id: 1, name: "bbb", age: 25}]

• _.pick：根据第二个参数的key的数组，筛选第一个参数中的值并返回

var foo = {id: 0, name: "aaa", age: 33}
var bar = _.pick(foo, ['name', 'age'])
//bar = {name: "aaa", age: 33}

• _.keys：返回object中的所有key

var foo = {id: 0, name: "aaa", age: 33}
var bar = _.keys(foo)
//bar = ['id', 'name', 'age']

• _.cloneDeep：深度拷贝，这个不用多说了吧，js中基础类型以外的类型，都会默认拷贝备份

var foo = {id: 0, name: "aaa", age: 33}
var bar = _.cloneDeep(foo)

• _.find：查找数组（注意一下如果没找到的话，会返回undefined，要处理一下）

var foo = [
{id: 0, name: "aaa", age: 33},
{id: 1, name: "bbb", age: 25}
] 
var bar = _.find(foo, ['id', 0])
//bar = {id: 0, name: "aaa", age: 33}

• _.keyBy：以某个属性为键，将数组转为对象

var foo = var foo = [
{id: 0, name: "aaa", age: 33},
{id: 1, name: "bbb", age: 25}
]
var bar = _.keyBy(foo, 'name')
//bar = {
//    aaa: {id: 0, name: "aaa", age: 33},
//    bbb: {id: 1, name: "bbb", age: 25}
//}

• _.filter：根据条件过滤出符合条件的元素，返回新数组

var foo = var foo = [
{id: 0, name: "aaa", age: 33},
{id: 1, name: "bbb", age: 25}
]
var bar = _.filter(foo, ['name', "aaa"])
//bar = {
//    aaa: {id: 0, name: "aaa", age: 33}
//}

• _.map：从集合中挑出一个key，将其值作为数组返回

var foo = var foo = [
{id: 0, name: "aaa", age: 33},
{id: 1, name: "bbb", age: 25}
]
var bar = _.map(foo, 'name')
//bar = ["aaa", "bbb"]

• .max/.min/_.sum：数组中最大值、最小值、数组求和

var foo = [1, 2, 3, 4]
var bar = _.max(foo)
//bar = 4
bar = _.min(foo)
//bar = 1
bar = _.sum(foo)
//bar = 10

• .pad/.padStart/_.padEnd：在两端、开头、末尾补齐字符

var foo = "helloworld"
var bar = _.pad(foo, 14, '-')
//bar = --helloworld--
bar = _.padStart(foo, 14, '-')
//bar = ----helloworld
bar = _.padEnd(foo, 14, '-')
//bar = helloworld----

• 组合用法
• 选出json数组中id最大的一项

var foo = [
{id: 0, name: "aaa", age: 33},
{id: 1, name: "bbb", age: 25}
]
var bar = _.find(foo, ['id', _.max(_.map(foo, 'id'))])
// bar = {id: 1, name: "bbb", age: 25}
// ps:也可以用maxBy某个key来代替

• 更新json数组中某一项的值

var foo = [
{id: 0, name: "aaa", age: 33},
{id: 1, name: "bbb", age: 25}
]
let list = _.keyBy(foo, 'id')
list[0].name = "ccc"
var bar = _.map(list)
// bar = [
//    {id: 0, name: "ccc", age: 33},
//    {id: 1, name: "bbb", age: 25}
//]