首页 \ 问答 \ javascript forEach方法有什么用途(该地图无法做什么)?(what use does the javascript forEach method have (that map can't do)?)

javascript forEach方法有什么用途(该地图无法做什么)?(what use does the javascript forEach method have (that map can't do)?)

我在map和foreach中看到的唯一区别就是map返回一个数组,而forEach不是。 但是,我甚至不理解forEach方法的最后一行“ func.call(scope, this[i], i, this); ”。 例如,不是“ this ”和“ scope ”是指同一个对象,而不是this[i] ,而是指循环中的当前值?

我注意到另一个帖子有人说“使用forEach当你想在列表的每个元素的基础上做某事时,你可能会在页面中添加东西,例如,基本上,当你想要”副作用“我不知道副作用是什么意思。

Array.prototype.map = function(fnc) {
    var a = new Array(this.length);
    for (var i = 0; i < this.length; i++) {
        a[i] = fnc(this[i]);
    }
    return a;
}

Array.prototype.forEach = function(func, scope) { 
    scope = scope || this; 
    for (var i = 0, l = this.length; i < l; i++) {
        func.call(scope, this[i], i, this); 
    } 
}

最后,javascript中是否有这些方法的真正用途(因为我们不更新数据库),而是像这样操纵数字:

alert([1,2,3,4].map(function(x){ return x + 1})); //this is the only example I ever see of map in javascript.

感谢任何回复。


The only difference I see in map and foreach is that map is returning an array and forEach is not. However, I don't even understand the last line of the forEach method "func.call(scope, this[i], i, this);". For example, isn't "this" and "scope" referring to same object and isn't this[i] and i referring to the current value in the loop?

I noticed on another post someone said "Use forEach when you want to do something on the basis of each element of the list. You might be adding things to the page, for example. Essentially, it's great for when you want "side effects". I don't know what is meant by side effects.

Array.prototype.map = function(fnc) {
    var a = new Array(this.length);
    for (var i = 0; i < this.length; i++) {
        a[i] = fnc(this[i]);
    }
    return a;
}

Array.prototype.forEach = function(func, scope) { 
    scope = scope || this; 
    for (var i = 0, l = this.length; i < l; i++) {
        func.call(scope, this[i], i, this); 
    } 
}

Finally, are there any real uses for these methods in javascript (since we aren't updating a database) other than to manipulate numbers like this:

alert([1,2,3,4].map(function(x){ return x + 1})); //this is the only example I ever see of map in javascript.

Thanks for any reply.


原文:https://stackoverflow.com/questions/3034392
更新时间:2022-02-23 21:02

最满意答案

@WebResult(name="basicGroup")这不是你的WSDL的一部分,因为它被标记为XmlTransient

@XmlTransient
private BasicGroup basicGroup;

所以它将无法挑选出你的回应的那部分。


@WebResult(name="basicGroup") this is not part of your WSDL since it's marked as XmlTransient:

@XmlTransient
private BasicGroup basicGroup;

So it won't be able to pick out that part of for your response.

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