JavaScript Closure Getting Started Example_Basic Knowledge

1.

Copy code The code is as follows:

functionsay667(){
varnum=666;
varsayAlert=function(){alert(num);}
num ;
returnsayAlert;
}

varsayAlert=say667();
sayAlert();

2.

Copy code The code is as follows:

functionsetUpSomeGlobals(){
varnum=666;
gAlertNumber=function(){alert(num);}
gIncreaseNumber=function(){num ;}
gSetNumber=function(x){num=x;}
}

setUpSomeGlobals();//Assign values ​​to three global variables
gAlertNumber();//666
gIncreaseNumber();
gAlertNumber();//667
gSetNumber(12);
gAlertNumber();//12

3.

Copy code The code is as follows:

functionbuildList(list){
varresult=[];
for(vari=0;ivariiteml='item' list[i];
result.push(function(){alert( item '' list[i]);});
}
returnresult;
}

functiontestList(){
varfnlist=buildList([1,2,3]);
for(varj=0;jfnlist[j]() ;
}
}

4.

Copy code The code is as follows:

functionsayAlice(){
varsayAlert=function(){alert(alice);}
varalice='HelloAlice';
returnsayAlert;
}

varhelloAlice=sayAlice();
helloAlice();//HelloAlice

5.

Copy code The code is as follows:

functionnewClosure(someNum,someRef){
varnum=someNum;
varanArray=[1,2,3];
varref=someRef;
returnfunction(x){
num =x;
anArray.push(num );
alert('num:' num 'nanArray' anArray.toString() 'nref.someVar' ref.someVar);
}
}

closure1=newClosure(40,{someVar:'closure1'});
closure2=newClosure(1000,{someVar:'closure2'});

closure1(5);
closure2(-10);