Javascript：.push 不是函数

Javascript: .push is not a function

提问by Devilius

I am having a problem with my code:

我的代码有问题：

var arrays = [[1, 2, 3], [4, 5], [6]];
console.log(reduce(arrays,function(array,b){
  return array.push(b);
}));

function reduce(array,combine){
  var current = [];
  for(var i = 0;i<array.length;i += 1){
    current = combine(current,array[i]);
  }
  return current;
}
console.log(reduce([1, 2, 3, 4], function(array, b) {
  return array.push(b);
}));

// → [1, 2, 3, 4, 5, 6]

I get this error:

我收到此错误：

TypeError: array.push is not a function (line 3) 

As far as I understand, this is because it is treating the array argument as something other than an array. However, I thought I fed it the variable "current" which is an array. Can someone explain the problem? Thanks.

据我了解，这是因为它将数组参数视为数组以外的东西。但是，我想我给它输入了变量“current”，它是一个数组。有人可以解释这个问题吗？谢谢。

回答by Rocket Hazmat

Array.pushdoesn't return an array. It returns the newlength of the array it was called on.

Array.push不返回数组。它返回调用它的数组的新长度。

So, your return array.push(b);returns an int. That int gets passed back as array... which is not an array so it doesn't have a .push()method.

因此，您return array.push(b);返回一个int. 该 int 被传回为array... 这不是数组，因此它没有.push()方法。

You need to do:

你需要做：

array.push(b);
return array;

回答by Leon Gaban

Return just the Array, see below:

只返回数组，见下文：

http://jsfiddle.net/0en82r7t/1/

http://jsfiddle.net/0en82r7t/1/

var arrays = [[1, 2, 3], [4, 5], [6]];
console.log(reduce(arrays,function(array,b){
  array.push(b);
  return array;
}));

function reduce(array,combine){
  var current = [];
  for(var i = 0;i<array.length;i += 1){
    current = combine(current,array[i]);
  }
  return current;
}
console.log(reduce([1, 2, 3, 4], function(array, b) {
  array.push(b)
  return array;
}));

array.push does not return an Array, but instead the new length

array.push 不返回数组，而是返回新长度

Also, I know this is just a test, but in the future and in real app development don't name an Arrayarray. Use more verbose and clear naming, examples: numGroupArray, datesArray, timeArray, tagsArray...

另外，我知道这只是一个测试，但在未来和实际应用程序开发中不要命名Array数组。使用更详细和清晰的命名，例如：numGroupArray、datesArray、timeArray、tagsArray...

回答by sfandler

The problem here is that array.push(b)returns the new length of the array. So after calling combine(current, array[i])for the first time, the length of your array will be returned and currentbecomes an integer, and since currentis the passed to combine(current, array[i])in the next iteration, JavaScript throws the TypeError. Your implementation for combine(current, array[i]should look like this:

这里的问题是array.push(b)返回array. 所以在combine(current, array[i])第一次调用之后，你的数组的长度将被返回并current变成一个integer，并且由于current是combine(current, array[i])在下一次迭代中传递给，JavaScript 抛出TypeError. 您的实现combine(current, array[i]应如下所示：

function(array, b) {
    array.push(b);
    return array;
}

回答by Youssef

ES6 solution :

ES6 解决方案：

reduce([1, 2, 3, 4], (array, b) => [...array, b], [])

回答by Sushant Kafle

Looks like there is a problem in your implementation:

看起来你的实现有问题：

function(array, b) {
  return array.push(b);
}

What you are returning from this function is not a array.

您从此函数返回的不是数组。

return array.push(b);

returns the length of the array after performing the push.

执行推送后返回数组的长度。

So, you should modify your function to:

因此，您应该将函数修改为：

function(array, b) {
  array.push(b);
  return array;
}

This might do the trick. Goodluck!

这可能会奏效。祝你好运！

回答by Justin Schultz

I don't understand what the function reduce is doing, but the problem is that Array.prototype.push returns the length of the array.

我不明白 reduce 函数在做什么，但问题是 Array.prototype.push 返回数组的长度。

var array = [1,2,'b'];
var val = array.push('foo');
// val === 4;

Therefore, instead of re-setting current every iteration of your loop, just simply call the function since .push()modifies the array in place.

因此，无需在循环的每次迭代中重新设置当前值，只需简单地调用该函数即可，因为它.push()会就地修改数组。

function reduce(array,combine){
  var current = [];
  for(var i = 0;i<array.length;i += 1){
    combine(current,array[i]);
  }
  return current;
}