let a=9const a=1var a=6c=5

//函數(shù)聲明function say(){  console.log('hello') }//函數(shù)表達(dá)式var say=function (){  console.log('hello') }

/*** 正確的方式：先聲明函數(shù)，再調(diào)用函數(shù) (最佳實(shí)踐)*/function catName(name) {  console.log("我的貓名叫 " + name);}catName("Tigger");/*以上代碼的執(zhí)行結(jié)果是: "我的貓名叫 Tigger"*//*** 不推薦的方式：先調(diào)用函數(shù)，再聲明函數(shù) */catName("Chloe");function catName(name) {  console.log("我的貓名叫 " + name);}/*代碼執(zhí)行的結(jié)果是: "我的貓名叫 Chloe"*/

/**demo1**/console.log('a=',a) //a=undefinedconsole.log('b=',b) // Uncaught ReferenceError: b is not definedvar a=1b=6/**deom2**/console.log('a=',a) // a=function a() {console.log("func a()")}function a() {console.log("func a()")}/**deom3**/console.log('a=',a) // a=function a() {console.log("fun a")}var a=3var a=4function a(){console.log("fun a")}var a=5var a=6console.log("a=",a) // a=6 /**deom4**/console.log('a=',a) // a=undefinedvar a =2console.log('a=',a) //var a =3var a =4console.log('a=',a) // a=4console.log('b=',b) //b= undefinedvar b='b1'/**deom5**/console.log('a=',a) // a=function a() {console.log("a2")}function a(){console.log("a1")}function a(){console.log("a2")}console.log('a=',a) // a=function a() {console.log("a2")}/**deom6**/console.log('a=',a) // a=undefinedvar a=function(){console.log('a1')}var a=3var a=4var a=5console.log(a)var a=function(){console.log('a2')}console.log('a=',a) // a= ƒ (){console.log('a2')}/**deom7**/console.log('b=',b)var a=3function b(i){  console.log('a=',a)  var a=4  function a(){    console.log('fun a')  }  console.log('a=',a)}b()/**demo8**/console.log('a=',a) //a= function a(){ console.log('fun a')}var a=2function a(){  console.log('fun a')}console.log('a=',a) // a=2var a=3var a=4var a=5console.log('a=',a) // a=5/**demo9**/console.log('a=',a) //Uncaught ReferenceError: a is not definedlet a=4/****/<!--demo10-->console.log('b=',b) // Uncaught ReferenceError: b is not definedconst b=5