博客

1、使用Array.includes处理多种条件

function test(fruit) {
    if (fruit == 'apple' || fruit == 'strawberry') {
    console.log('red');
}}

function test(fruit) {
    const redFruits = ['apple', 'strawberry', 'cherry', 'cranberries'];
    if (redFruits.includes(fruit)) {
        console.log('red');
    }
}

2、减少嵌套，尽早return

function test(fruit, quantity) {
  const redFruits = ['apple', 'strawberry', 'cherry', 'cranberries'];
  if (fruit) {
    if (redFruits.includes(fruit)) {
      console.log('red');
      if (quantity > 10) {
        console.log('big quantity');
      }
    }
  } else {
    throw new Error('No fruit!');
  }
}
test(null); // error: No fruits
test('apple'); // print: red
test('apple', 20); // print: red, big quantity

function test(fruit, quantity) {
  const redFruits = ['apple', 'strawberry', 'cherry', 'cranberries'];
  if (!fruit) throw new Error('No fruit!');
  if (redFruits.includes(fruit)) {
    console.log('red');
    if (quantity > 10) {
      console.log('big quantity');
    }
  }
}

function test(fruit, quantity) {
  const redFruits = ['apple', 'strawberry', 'cherry', 'cranberries'];
  if (!fruit) throw new Error('No fruit!'); 
  if (!redFruits.includes(fruit)) return; 
  console.log('red');
  if (quantity > 10) {
    console.log('big quantity');
  }
}

3、使用函数默认参数和解构

function test(fruit, quantity) {
  if (!fruit) return;
  const q = quantity || 1; 
  console.log(`We have ${q} ${fruit}!`);
}
test('banana'); // We have 1 banana!
test('apple', 2); // We have 2 apple!

function test(fruit, quantity = 1) { 
  if (!fruit) return;
  console.log(`We have ${quantity} ${fruit}!`);
}
test('banana'); // We have 1 banana!
test('apple', 2); // We have 2 apple!

function test(fruit) { 
  if (fruit && fruit.name)  {
    console.log (fruit.name);
  } else {
    console.log('unknown');
  }
}
test(undefined); // unknown
test({ }); // unknown
test({ name: 'apple', color: 'red' }); // apple

function test({name} = {}) {
  console.log (name || 'unknown');
}
test(undefined); // unknown
test({ }); // unknown
test({ name: 'apple', color: 'red' }); // apple
// 在执行test(undefined)这行代码时就会报错：无法解析’undefined’或’null’的属性name，因为undefined没有name这个属性

function test(fruit) {
  console.log(__.get(fruit, 'name', 'unknown'); 
}
test(undefined); // unknown
test({ }); // unknown
test({ name: 'apple', color: 'red' }); // apple

4、对所有或部分规则使用Array.every和Array.some

const fruits = [
    { name: 'apple', color: 'red' },
    { name: 'banana', color: 'yellow' },
    { name: 'grape', color: 'purple' }
  ];
function test() {
  let isAllRed = true;
  for (let f of fruits) {
    if (!isAllRed) break;
    isAllRed = (f.color == 'red');
  }
  console.log(isAllRed); // false
}

const fruits = [
    { name: 'apple', color: 'red' },
    { name: 'banana', color: 'yellow' },
    { name: 'grape', color: 'purple' }
  ];
function test() {
  const isAllRed = fruits.every(f => f.color == 'red');
  console.log(isAllRed); // false
}

const fruits = [
    { name: 'apple', color: 'red' },
    { name: 'banana', color: 'yellow' },
    { name: 'grape', color: 'purple' }
];
function test() {
  const isAnyRed = fruits.some(f => f.color == 'red');
  console.log(isAnyRed); // true
}