# js

**Repository Path**: flyation/js

## Basic Information

- **Project Name**: js
- **Description**: No description available
- **Primary Language**: HTML
- **License**: Not specified
- **Default Branch**: master
- **Homepage**: None
- **GVP Project**: No

## Statistics

- **Stars**: 0
- **Forks**: 0
- **Created**: 2020-08-15
- **Last Updated**: 2021-11-02

## Categories & Tags

**Categories**: Uncategorized

**Tags**: None

## README

# js类型转换
## xxx 2 boolean
```javascript
if (xxx) {
    alert(true)
} else {
    alert(false)
}
```
### undefined、null 2 boolean
undefined: false  
null: false  
### number 2 boolean
非0: true  
Infinity/-Infinity: true  
0: false  
NaN: false
### string 2 boolean
非'': true  
'': false
### [ ] 2 boolean
always true  
**结论：数组无法通过转布尔来判断属性的数量是否为0**
### { } 2 boolean
always true  
**结论：对象无法通过转布尔来判断长度是否为0**