js中map用法

let newArray = array.map(function(currentValue, index, arr) {
  // 返回经过操作后的值
});

let newArray = array.map(currentValue => {
  // 返回经过操作后的值
});

let numbers = [1, 2, 3, 4, 5];

let squares = numbers.map(function(number) {
  return number * number;
});

// 使用箭头函数简化
let squaresArrow = numbers.map(number => number * number);

console.log(squares); // 输出: [1, 4, 9, 16, 25]
console.log(squaresArrow); // 输出: [1, 4, 9, 16, 25]

let numbers = [1, 2, 3, 4, 5];

// 错误的示例，当number为2时没有返回值
let result = numbers.map(function(number) {
  if (number === 2) {
    // 没有返回值
  }
  return number * number;
});

console.log(result); // 输出: [1, undefined, 9, 16, 25]

// 正确的示例
let correctResult = numbers.map(function(number) {
  if (number === 2) {
    return number * number; // 确保所有路径都有返回值
  }
  return number * number;
});

console.log(correctResult); // 输出: [1, 4, 9, 16, 25]