问题描述
这帮助我理解了很多,但我有一个小问题:
当我插入数组时,它正常工作,但对象不起作用。我弄不明白。对于我应该改变的内容,我将不胜感激。我评论了我认为应该改变的地方,但我很困惑我需要改变它。我也创建了我自己的每个功能。
你可以在这里找到我的代码:
任何建议都会非常有帮助。谢谢!!
这是我到目前为止:
var myArray = [1,2,3,4,5];
var myObject = {
num1:1,
num2:2,
num3:3
};
函数each(collection,callback){
if(Array.isArray(collection)){
for(var i = 0,l = collection.length; i callback(collection [i]);
};
} else if(collection ===object){
for(var collection in collection){
callback(collection [prop]);
};
}
}
函数multiply(num,num2){
return num * num2;
函数reduce(collection,callback,accumulator){
each(collection,function(element){
if(accumulator === undefined){
return accumulator = element; //这里是问题吗?为什么?我不明白。
} else {
return accumulator = callback(accumulator,element);
};
});
返回累加器;
};
console.log(reduce(myArray,multiply)); // 120
console.log(reduce(myArray,multiply,5)); // 160
console.log(reduce(myObject,multiply)); //返回undefined
console.log(reduce(myObject,multiply,5)); //返回5
if(collection ===object)
$ c $ if(typeof(集合)===object)
以下是固定代码:
var myArray = [1,2,3,4,5];
var myObject = {
num1:1,
num2:2,
num3:3
};
函数each(collection,callback){
if(Array.isArray(collection)){
for(var i = 0,l = collection.length; i callback(collection [i]);
};
} else if(typeof(collection)===object){
for(var collection in collection){
callback(collection [prop]);
};
}
}
函数multiply(num,num2){
return num * num2;
函数reduce(collection,callback,accumulator){
each(collection,function(element){
if(accumulator === undefined){
return accumulator = element; //这里是问题吗?为什么?我不明白。
} else {
return accumulator = callback(accumulator,element);
};
});
返回累加器;
};
console.log(reduce(myArray,multiply)); // 120
console.log(reduce(myArray,multiply,5)); // 600
console.log(reduce(myObject,multiply)); // 6
console.log(reduce(myObject,multiply,5)); // 30
I'm trying to recreate the reduce method but as the original function.
This helped me to understand a lot but I have one little issue:How to re-create Underscore.js _.reduce method?When I plug in arrays it works right, but objects don't work. I get undefined. I would appreciate advice on what I should change. I commented where I think I should change something but I'm confused exactly what I need to change it to. I also created my own each function.
You can find my code here: http://goo.gl/6RU9Bc
Any advice would be super helpful. Thank you!!
This is what I have so far:
var myArray=[1,2,3,4,5];
var myObject={
num1:1,
num2:2,
num3:3
};
function each(collection, callback){
if(Array.isArray(collection)) {
for(var i=0, l=collection.length; i<l; i++){
callback(collection[i]);
};
}else if(collection === "object") {
for(var prop in collection){
callback(collection[prop]);
};
}
}
function multiply(num, num2){
return num*num2;
}
function reduce(collection, callback, accumulator){
each(collection, function(element){
if(accumulator === undefined) {
return accumulator = element; // is the problem here? Why? I don't understand.
}else {
return accumulator = callback(accumulator, element);
};
});
return accumulator;
};
console.log(reduce(myArray, multiply)); // 120
console.log(reduce(myArray, multiply, 5)); // 160
console.log(reduce(myObject, multiply)); // returns undefined
console.log(reduce(myObject, multiply, 5)); // returns 5
解决方案 As pointed out by @Yeldar Kurmangaliyev, you need to change this:
if(collection === "object")
to:
if(typeof(collection) === "object")
Here is the fixed code:
var myArray=[1,2,3,4,5];
var myObject={
num1:1,
num2:2,
num3:3
};
function each(collection, callback){
if(Array.isArray(collection)) {
for(var i=0, l=collection.length; i<l; i++){
callback(collection[i]);
};
}else if(typeof(collection) === "object") {
for(var prop in collection){
callback(collection[prop]);
};
}
}
function multiply(num, num2){
return num*num2;
}
function reduce(collection, callback, accumulator){
each(collection, function(element){
if(accumulator === undefined) {
return accumulator = element; // is the problem here? Why? I don't understand.
}else {
return accumulator = callback(accumulator, element);
};
});
return accumulator;
};
console.log(reduce(myArray, multiply)); // 120
console.log(reduce(myArray, multiply, 5)); // 600
console.log(reduce(myObject, multiply)); // 6
console.log(reduce(myObject, multiply, 5)); // 30
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