ES6 - 箭头函数和扩展

// 主动抛出异常
function add(a,b = 1){
    if(a == 0){
        throw new Error('A is Error');
    }
    return a+b;
}
console.log(add(0));

function add(a,b = 1){
    if(a == 0){
        throw new Error('A is Error');
    }
    return a+b;
}

// 获取函数参数个数
console.log(add.length);    //  返回1，返回必须传递的参数个数，此处是a

箭头函数

var add = (a,b = 1) => a + b;
document.write(add(1));

var add = (a,b = 2) => {
    document.write('js')
    return a + b;
}
document.write(add(2));