generat中的Javascript闭包

Question

var generateID=function() {
    var prefix="uid-";
    var count=0;

    return function(){
        count+=1;
        console.log(prefix+count)
    }
}
var create = generateID();

console.log(create());
console.log(create());
console.log(create());

预期产出: uid-1 uid-2 uid-3

帮助我在未定义的错误部分输出。

Answer 1

创建不返回任何内容，因此如果console.log(create())打印未定义的

​

var generateID=function() {
    var prefix="uid-";
    var count=0;

    return function(){
        count+=1;
        console.log(prefix+count)
    }
}
var create = generateID();

create()
create()
create()

var generateID2 = function() {
    var prefix="uid-";
    var count=0;

    return function(){
        count+=1;
        return prefix+count
    }
}
var create2 = generateID2();

console.log(create2())
console.log(create2())
console.log(create2())

​

Answer 2

create函数不返回任何值。这就是为什么console.log(create());调用日志undefined的原因。

return function() {
    count+=1;
    return prefix+count;
}