都说不会“懒惰”的工程师不是一个好程序员，今天分享一下，这几年来代码优化总结

1. 多个if条件判断

NORMAL:

if (x === 'Tom' || x === 'Jerry' || x === 'Daniel' || x ==='Jack') {}

BETTER:

if (['Tom', 'Jerry', 'Daniel', 'Jack'].includes(x)) {}

2. if…else…

NORMAL:

let isOverTen: boolean;
if (x > 10) {
    isOverTen = true;
} else {
    isOverTen = false;
}

BETTER:

let isOverTen = x > 10;

3. 检查 value 是否是 Null, Undefined, null

NORMAL:

let second = '';
if (first !== null || first !== undefined || first !== '') {
    second = first;
}

BETTER:

let second = first || '';

4. For 循环

NORMAL:

for (var i = 0; i < testData.length; i++)

BETTER:

for (let i in testData)
// or
for (let i of testData)

5. Function 条件调用

NORMAL:

function method1() {
  console.log('call method1');
};
function method2() {
  console.log('call method2');
};
let text = 1;
if (text == 1) {
  method1();
} else {
  method2();
}

BETTER:

(text === 1? method1:method2)();

6. switch 表达式

NORMAL:

switch (data) {
  case 1:
    test1();
  break;
  case 2:
    test2();
  break;
  case 3:
    test();
  break;
  // so on...
}

BETTER:

var data = {
  1: test1,
  2: test2,
  3: test
};
data[case] && data[case]();

7. 多行 String

NORMAL:

const data = 'abc abc abc abc abc abc\n\t'
    + 'test test,test test test test\n\t'

BETTER:

const data = `abc abc abc abc abc abc
         test test,test test test test`

8. 隐式返回

NORMAL:

function getArea(diameter) {
  return Math.PI * diameter
}

BETTER:

const getArea = diameter => Math.PI * diameter;

9. 迭代重复

NORMAL:

let text = ''; 
for(let i = 0; i < 5; i ++) { 
  text += 'text '; 
} 

BETTER:

'text '.repeat(5);

10. 幂运算

NORMAL:

Math.pow(2,3);

BETTER:

2**3 // 8

11. Foreach 循环

NORMAL:

const array1 = ['a', 'b', 'c'];
array1.forEach(function (element){
  console.log(element)
});

BETTER:

const array1 = ['a', 'b', 'c'];
for (let element in array1){
  console.log(element)
}