JavaScript深入学习之作用域与作用域链

function func() {
    implyGlobalVar = 'global';
    var localVar = 'local'
}
func() // 执行
console.log(implyGlobalVar) // global
console.log(localVar)       // localVar is not defined
复制代码

function foo() {
    var localVar = 'local'
    function localFunc() {
        console.log(local)
    }
    localFunc() // local
}
localFunc() // 报错
复制代码

function foo() {
    var localInnerVar = 'localInner'
    function localFunc() {
        console.log(local)
    }
    localFunc() // localInner
}
复制代码

if (1) {
    var a = 10
}
console.log(a) // 10
复制代码

console.log(b) // undefined
console.log(a) // Uncaught ReferenceError: a is not defined
let a = 'i am there'
var b = 'i am here'
复制代码

console.log(a) // Identifier 'a' has already been declared
var a = 'the first'
let a = 'the second'
复制代码

var arr = [];
for (var i = 0; i < 10; i++) {
    arr[i] = function() {
        console.log(i);
    }
}
arr[0]() // 10
复制代码

var arr = [];
for (var i = 0; i < 10; i++) {
    (function (i) {
        arr[i] = function() {
            console.log(i);
        }
    }(i))
}
arr[0]() // 0
复制代码

var arr = [];
for (let i = 0; i < 10; i++) {
    arr[i] = function() {
        console.log(i);
    }
}
arr[0]() // 0
复制代码

function foo() {
    function bar() {
        var inner = 234;
        outer = 0;
        console.log(inner);
    }
    var outer = 123;
    bar();
    console.log(outer)
    console.log(glob)
}
var glob = 100;
foo()
复制代码

var foo = 1;
function bar() {
    console.log(foo);  //undefined
    if (!foo) {
        var foo = 10;
    }
    console.log(foo); //10
}
bar();
复制代码

var a = 1;
function b() {
    console.log(a);  // fn
    a = 10;
    return;
    function a() { }
}
b();
console.log(a); //1
复制代码

console.log(foo); //fn  C
var foo = "A";
console.log(foo)  //A
var foo = function () {
    console.log("B");
}
console.log(foo); //fn  B
foo(); // B
function foo(){
    console.log("C");
}
console.log(foo)  //fn B
foo(); // B
复制代码

var foo = 1;
function bar(a) {
    var a1 = a;
    var a = foo;
    function a() {
        console.log(a); //1
    }
    a1();
}
bar(3);
复制代码