JavaScript 排序比较器函数
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JavaScript sort comparator function
提问by Stanimirovv
Basically I want to build a function which sorts objects in an array by one of the object's properties/member variables. I am preeeety sure that the comparator function is where the error is hidden, but I am not 100% sure.
基本上我想构建一个函数，通过对象的属性/成员变量之一对数组中的对象进行排序。我很确定比较器函数是隐藏错误的地方，但我不是 100% 确定。
The output I should get after the sort function is called is 1,2,3. I get 1,3,2which means that it is unchanged
调用排序函数后我应该得到的输出是1,2,3. 我明白1,3,2这意味着它没有改变
This is the entire js code (with some comments):
这是整个js代码（有一些注释）：
var arr = [];
//object definition and creation
var main = document.getElementById("main");
var task = {
name: "",
priority: 0
};
//first
var one = Object.create(task);
one.priority = 1;
//secondd
var two = Object.create(task)
two.priority = 3;
//last
var three = Object.create(task);
three.priority = 2;
//append
arr.push(one);
arr.push(two);
arr.push(three);
//sort function
function sortT() {
arr.sort(compareFN);
}
//comperator function
function compareFN() {
return task.priority < task.priority;
}
function print() {
for (var i = 0; i < arr.length; i++) {
console.log(arr[i].priority);
}
}
//execution of the program
print();
sortT();
print();
EDIT: The solution is the following - As stated, the comparator function really was the problem, the correct way to write it is the following:
编辑：解决方案如下 - 如前所述，比较器功能确实是问题所在，正确的编写方法如下：
function compareFN(taskA, taskB) {
return taskA.priority < taskB.priority;
}
回答by robbi5
The compare function needs two arguments: the first and the second element it should compare. So your compareFN should look like this:
compare 函数需要两个参数：它应该比较的第一个和第二个元素。所以你的 compareFN 应该是这样的：
function compareFN(taskA, taskB) {
return taskA.priority - taskB.priority;
}
Edit: As NPE said, it is supposed to perform a three-way comparison, so a simple a < bis not so a great idea here.
回答by NPE
There are multiple problems with your comparator:
您的比较器存在多个问题：
- It refers to the global
taskobject instead of the objects being compared. - It compares the object to itself.
- It is supposed to perform a three-way comparison.
- 它指的是全局
task对象而不是被比较的对象。 - 它将对象与自身进行比较。
- 它应该执行三向比较。
Try:
尝试：
var compareFN = function(a, b) {
return a.priority - b.priority;
}
回答by dougajmcdonald
You need to change the signature of you compare function to include the two tasks.
您需要更改比较函数的签名以包含这两个任务。
For ascending order (normally what you want) you need to do b < a, a < b will do descending order
对于升序（通常是您想要的），您需要执行 b < a，a < b 将执行降序
//comperator function
function compareFN(a, b) {
return b.priority < a.priority;
}
回答by GilbertS
The comparator function returns a negative value, zero or a positive value. Those three comprise what is called here the three-way comparison. So: ''' function cmp((a, b) => { // ascending return a - b } ''' For descending return b - a
比较器函数返回负值、零或正值。这三个构成了这里所说的三向比较。所以： ''' function cmp((a, b) => { // 升序返回 a - b } ''' 降序返回 b - a
