映射函数js断言测试中的forEach未运行

Question

我目前正在为map/ cubeAll函数进行断言测试。我已经多次修改了我的逻辑和语法，我还没有发现为什么编译器会抛出一个"Type array.forEach不是一个函数“错误。我读过关于TypeError错误的MDN页面，我知道我的“forEach”试图从一个函数调用一个值，并且Array.prototype.forEach需要一个回调函数才能正常工作。根据我的逻辑，在我的代码(下面)中，我确实有一个回调函数，并且我试图通过将数组中的每个元素传递回这个调用来调用一个值。怎么啦？

function map(array, callbackFunction) {
  var newArray = [];
  array.forEach(function(element) {
    newArray.push(callbackFunction(element));
  });
  return newArray;
}

function cubeAll(numbers) {
  return map(numbers, function(n) {
    return n * n * n;
  });
}

function assertArraysEqual(actual, expected, testName) {
  let arraysHaveEqualLength = actual.length === expected.length;
  let arraysHaveSameElements = actual.every(function(ele,idx){
    return ele === expected[idx];
  });
  if(arraysHaveEqualLength && arraysHaveSameElements){
    console.log(`${testName} has passed.`);
  }else {
    console.log(`${testName} has FAILED. Expected ${expected} and got ${actual} instead.`);
  }
}

我试着测试的案例：

assertArraysEqual(map([3,2,1],cubeAll),[27,8,1], 'it should return a new array with all the elements cubed');
assertArraysEqual(map([3,2,1],cubeAll),[27,7,1], 'it should return a new array with all the elements cubed');

控制台中的错误：

 array.forEach(element => newArray.push(callbackFunction(element)));
        ^

TypeError: array.forEach is not a function

谢谢!

Answer 1

函数cubeAll接收一个数字而不是一个数组。

function cubeAll(n) {
    return n * n * n;
}

您可以使用内置对象Math和函数.pow(...)。

return Math.pow(n, 3);

对于支持ES2016的环境(常绿浏览器，节点7+)

function cubeAll(n) {
    return n ** 3;
}

​

function map(array, callbackFunction) {
  var newArray = [];
  array.forEach(function(element) {
    newArray.push(callbackFunction(element));
  });
  return newArray;
}

function cubeAll(n) {
  return n ** 3;
}

function assertArraysEqual(actual, expected, testName) {
  let arraysHaveEqualLength = actual.length === expected.length;
  let arraysHaveSameElements = actual.every(function(ele,idx){
    return ele === expected[idx];
  });
  if(arraysHaveEqualLength && arraysHaveSameElements){
    console.log(`${testName} has passed.`);
  }else {
    console.log(`${testName} has FAILED. Expected ${expected} and got ${actual} instead.`);
  }
}


assertArraysEqual(map([3,2,1],cubeAll),[27,8,1], 'it should return a new array with all the elements cubed');
assertArraysEqual(map([3,2,1],cubeAll),[27,7,1], 'it should return a new array with all the elements cubed');

​