12 - node access to file attributes - using a self-closure function call to solve the problem of lost i

The role of closure: Save Variable

A, i lost case

var arr = [ 'node', 'shock', 'mysql']

for(var i=0;i<arr.length;i++){　　

　　setTimeout(()=>{

　　　　console.log(arr[i])　　

　　},1000)

}

 

Second, the solution

Use closures: 

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

　　((i)=>{

　　　　setTimeout(()=>{

　　　　　　console.log(arr[i])

　　　　},1000)

　　})(i)

}