代码改变世界

y=y||'world'与y=y?y:'world'

2017-02-21 16:06  改吧  阅读(679)  评论(0)  编辑  收藏  举报
1.y=y||’world’
function log(x,y){
     y=y||’world’;
     console.log(x,y)
}
log(‘hello’)===>hello world
 log('hello','')==>hello world

 

 
 
 
2.y=y?y:'world'
function log(x,y){
     y=y?y:'world';
     console.log(x,y)
}
log('hello’)==>hello world
 log('hello','')==>hello world

 

 
 
 
3.传实参 
function log(x,y='world'){
console.log(x,y)
}

log('hello')===> hello world
log('hello','')==>hello