JavaScript循环内函数实现问题：自定义rep函数无法运行求助

Hey there, let's break down why your code isn't working and fix it up! Your implementation has two key issues that prevent it from populating the label array correctly:

1. You defined an arrow function but never executed it #

Inside your rep function's loop, you wrote i => { label.push(Unit ${i + 1}); } — this creates an arrow function, but you never actually run it! In the original example, the repeat function calls the passed-in action(i) to execute the callback logic. Without invoking that arrow function, nothing gets added to your array.

2. Your function is missing the callback parameter (breaking the original pattern) #

The original repeat function is designed to be flexible: it takes a number n and a callback function that defines what to do on each iteration. Your rep function only accepts n and hardcodes the arrow function inside, which not only deviates from the example's intent but also removes the flexibility of passing different actions.

Fixed Version (Matching the Original Example's Pattern) #

This fixes both issues by adding the callback parameter and actually invoking it in the loop:

function rep(n, action) { 
  for(let i = 0; i < n; i++){ 
    action(i); // Execute the callback with the current loop index
  } 
}

let label = [];
rep(5, i => { label.push(`Unit ${i + 1}`); }); // Pass your desired action as the callback
console.log(label); // Output: ["Unit 1", "Unit 2", "Unit 3", "Unit 4", "Unit 5"]

Simplified Version (If You Don't Need Callback Flexibility) #

If you just want to directly generate the array without using a callback, you can simplify the code like this (no need to define unused arrow functions):

function rep(n) { 
  const label = [];
  for(let i = 0; i < n; i++){ 
    label.push(`Unit ${i + 1}`); // Directly add items to the array in the loop
  } 
  return label;
}

console.log(rep(5)); // Output: ["Unit 1", "Unit 2", "Unit 3", "Unit 4", "Unit 5"]

内容的提问来源于stack exchange，提问作者Akash RP