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function show({x=0,y=0}={}){
console.log(x,y);
}
show()//不传参不会报错

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function show(a,b){
a = a || '欢迎';
b = b || 'mmr';
console.log(a,b);
}
show('welcome','牧码人');
show('welcome');
show('', '牧码人');
function show(a='欢迎',b='mmr'){
console.log(a,b);
}
show(,'牧码人');//此处后台会报错

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function show(a=18){
let a = 101;
//错误
console.log(a);
}
show()

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let show = (a,b)=>a+b;//此处相当于return a+b 的结果
console.log(show(12,5));
//另一种写法
let show = (a = 12, b = 5) => {
console.log(a, b);
return a + b;
};
show();

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let show = (...args) =>{
console.log(args);
//console.log(arguments);
}
show(1,2,3,4,5);

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let show = ()=>{
this.name='abc';
}
let s=new show();
alert(s.name);//会报错