小技巧

var ifRange = "123456";
var x = ~ifRange.indexOf(‘"‘) ? "45" :"66";
//66 x ~ifRange.indexOf(‘"‘)为0
console.log(x);

   MySQLStore.prototype.clone = function(object) {
        return JSON.parse(JSON.stringify(object));
   }

function A(){
}
var data = {};
A(data={
    x:"y"
});
//y
console.log(data.x);

function A(){
  var option ={
      a:"b"
  }; //x=undefined
  var option = [‘a‘]; //x=1
  console.log("x="+option.length);
}
A();

if(0){
  console.log("hello");
}else{
  console.log("kk");
}
//kk
var x = {};
console.log({}?"xx":"yy");
//xx

function B(){
    console.log("B");
    return "C";
}
function A(){
    return void B();
}

var x = A();
console.log("x=",x); //undefined
//如果去掉void，则x=C;