var a = 10;
function fn() {
a = 100;
console.log("函數(shù)內(nèi)的a:", a); //100
}
console.log("函數(shù)外的a:", a); //10
fn();
console.log("函數(shù)外的a:", a); //100
2.局部與全局的作用域區(qū)分
var a = 10;
function fn() {
var a = 100;
console.log(a); //100
}
fn();
console.log(a); //10
2.1 fn()內(nèi)重新聲明a將函數(shù)內(nèi)部的a變成了局部函數(shù)
var a = 10;
function fn() {
谜嫉、田晚、
a = 100;
console.log(a);//100
var a = 1332;
}
fn();
console.log(a);//10
3.
var a = 10;
function fn(a) {
//var a;
console.log(a);//undefined
a = 100;
console.log(a);//100
}
fn(10);
console.log(a);//10
4. a=100,變量提升，但是沒有var也沒有賦值邦邦，所以報錯
console.log(a); //err
a = 100;
console.log(a); //
function fn() {
a = 100;
console.log("我是函數(shù)里的a:", a); //
}
fn();
console.log("我是函數(shù)外的a:", a); //
5. a=b=10;會將b變成全局變量
var a = b = 10;
function fn() {
var a = b = 20;
console.log("函數(shù)內(nèi)：", a, b); //20,20
}
fn();
console.log("函數(shù)外", a, b);//10,20
6. c()里沒有a,往外找一層就找到全局的a
var a = 10;
function fn() {
var a = 100;
console.log("函數(shù)內(nèi)：", a);//100
c(); //10
// function b() {
// var a = 1000;
// c();
// }
// b();
}
function c() {
console.log("c里面的a", a);
}
fn();
7.c()往外找一層，就找到局部的a=100醉蚁；
var a = 10;
function fn() {
var a = 100;
console.log("函數(shù)內(nèi)：", a); //100
c();
function c() {
console.log("c里面的a", a); //100
}
}
fn();
console.log("函數(shù)外：", a);//10
