变量作用域

var a = 1
function test() {
    var a = 2
console.log(a) // 2
}
test()

var a = 1
function test2() {
    console.log(a) // undefined
var a = 2
}
test2()

var a = 1
function test3() {
    console.log(a) // 1
a = 2
}
test3()

let b = 1
function test4() {
    console.log(b) // b is not defined
let b = 2
}
test4()

function test5() {
    let a = 1
    console.log(a) // 1
    {
        let a = 2
    }
}
test5()

函数参数

function test6() {
    console.log(arguments) // [1,2]
}
test6(1,2)

function test7 () {
    return function () {
        console.log(arguments) // 未执行到此，无输出
    }
}
test7(1,2)

function test8 () {
    return function () {
        console.log(arguments) // [3,4]
    }
}
var fn = test8(1,2)

fn(3,4)

var args = [1,2]
function test9() {
    console.log(arguments) // [1,2,1,2]
}
Array.prototype.push.call(args,2)
test9(...args)

回调函数

function test10 (name,fn) {
    console.log(name)  // 'luozh'
    console.log(fn())  // 'zhuyj'
}
test10('luozh',function() {

return 'zhuyj'

})

对象拷贝与赋值

var obj = {
    name: 'luozh',age: 23
}
var newObj = obj
newObj.name = 'zhuyj'
console.log(obj) // Object {name: "zhuyj",age: 23}

console.log(newObj) // Object {name: "zhuyj",age: 23}

var obj2 = {
    name: 'luozh',age: 23
}
var newObj2 = Object.assign({},obj2,{color: 'blue'})
newObj2.name = 'zhuyj'
console.log(obj2) // Object {name: "luozh",age: 23}

console.log(newObj2) // Object {name: "zhuyj",age: 23,color: 'blue'}

var obj3 = {
    name: 'luozh',age: 23
}
var newObj3 = Object.create(obj3)
console.log(obj3) // Object {name: "luozh",age: 23}

console.log(newObj3.proto) // Object {name: "luozh",age: 23}