9.ES6 rest参数

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ES6 rest参数

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// ES6 引入 rest 参数，用于获取函数的实参，用来代替 arguments
// ES5 获取实参的方式
function test1() {
    console.log(arguments);
    /**
     * Arguments(3)
     * 0: "a"
     * 1: "b"
     * 2: "c"
     * callee: ƒ test1()
     * length: 3
     */
}
test1("a", "b", "c");

// rest 参数
function test2(...args) {
    console.log(args);
    /**
     * (3) ['i', 'j', 'k']
     * 0: "i"
     * 1: "j"
     * 2: "k"
     * length: 3
     */
}
test2("i", "j", "k");

let fn = (a, b, ...args) => {
    console.log(a);
    // 1
    console.log(b);
    // 2
    console.log(args);
    /**
     * (4) [3, 4, 5, 6]
     * 0: 3
     * 1: 4
     * 2: 5
     * 3: 6
     * length: 4
     */
}
fn(1,2,3,4,5,6);