Testing and Debugging

Unit test

function breakpoint

function sum(a, b){
  let result = a+ b;
  return result;
}
debug(sum) //注意这里传入函数对象
sum(1, 2); //执行sum函数时，会自动调用debugger

console.log
console.warn
console.error
console.group / console.groupEnd 在GA Debugger中经常见到的log输出，将相关的log放在同一组，可以折叠；组与组可以嵌套
console.assert 当断言结果为true，则不会输出任何log，为false则输出Asserion failed: xxx错误
```
console.assert(list.childNodes.length <= 500, "Node count is > 500");
```
console.dir 可以将DOM以js object的形式输出

Specifier	Output
%s	Formats the value as a string
%i or %d	Formats the value as an integer
%f	Formats the value as a floating point value
%o	Formats the value as an expandable DOM element. As seen in the Elements panel
%O	Formats the value as an expandable JavaScript object
%c	Applies CSS style rules to the output string as specified by the second parameter