1. 全局，function 内

function 内变量使用 var，重名时，局部变量的优先级更高

 1var a1 = 1;
 2(function() {
 3    a1 = 2;
 4    console.log(a1);  // 2
 5})();
 6console.log(a1);  // 2
 7
 8var a2 = 1, a3 = 1;
 9(function() {
10    var a2 = 2, a3;
11    console.log(a2);  // 2
12    console.log(a3);  // undefined
13})();
14console.log(a2);  // 1
15console.log(a3);  // 1

Compare with React and Vue

• React JSX

1const element = (
2  <h1 className="greeting">
3    Hello, world!
4  </h1>
5);

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const element = React.createElement(
  'h1',
  {className: 'greeting'},
  'Hello, world!'
);

Embrace async

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let af = () => promise;
let bf = () => promise;

let cf = () => {
  return af().then(() => {
    return bf().then(result => {
      let t = result;
      return ...;
    })
  });
}

let df = () => {
  cf().then().catch();
}

I think many guys are using express as they backend service framework, there is a most important thing Test. We should write test for the apis that usually contains a lot of business logics.

Today I want to show my experiences on writing test for express apis.

Configuration blocks and run blocks get executed at different points in the application bootstrap, and have different injection locals at their disposal. Here’s a summary of what you can find in the AngularJS documentation.