xgqfrms-GitHub/es6-arrow-functions-in-deepth.md

## es6-arrow-functions-in-deepth.md

      
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              es6-arrow-functions-in-deepth.md
            
          
    ES6 arrow-functions in deepth

https://wesbos.com/arrow-functions/
https://developer.mozilla.org/zh-CN/docs/Web/JavaScript/Reference/Functions/Arrow_functions#
const implicit = (a) => {
    a = a + 1;
    return a;
}


const implicitX = x => x = x + 1;


const implicit = (a) => {
    a = a + 1;
    let b = a * a;
    return b;
}


const implicitY = y => y = (y + 1) * (y + 1);

implicitY(2);
// 9

/* 当删除大括号时，它将是一个隐式的返回值，这意味着我们不需要指定我们返回*/


const implicitA = y => {y = (y + 1) * (y + 1);};

implicitA(2);
// undefined

/* 当有大括号时，我们需要指定返回一个显示的返回，*/


https://developer.mozilla.org/zh-CN/docs/Web/JavaScript/Reference/Functions/Arrow_functions#


// 如果箭头函数 有多个参数, 必须使用 ()圆括号:

const multi_params = (a, b) => {
    let sum = a + b;
    console.log(sum);
};


multi_params(1, 2);
// 3


// 如果箭头函数 无参数, 必须使用 ()圆括号或者 _下划线:


_ => { statements; }

const multi_X = _ => {
    let sum = a + b;
    console.log(sum);
};


multi_X(1, 2);
// Uncaught ReferenceError: a is not defined