var a=b=2 //相当于:
var a = 2;
b = 2;
function fn(){
var a = b = 2;
console.log(a,b); // 2 2
}
fn();
console.log(b) //2 b为全局变量
console.log(a); //a is not undefined a为局部变量
var a=b=2 //相当于:
var a = 2;
b = 2;
function fn(){
var a = b = 2;
console.log(a,b); // 2 2
}
fn();
console.log(b) //2 b为全局变量
console.log(a); //a is not undefined a为局部变量