JavaScript参数传递中值和引用的一种理解.docxVIP

值（value）和引用(reference)是各种编程语言老生常谈的话题，js也不例外。我将剖析一个例子的实际运行过程，跟大家分享我对js参数传递中的值和引用的理解。参考官网/en-US/docs/Web/JavaScript/Data_structures数据类型的两种分类，本文将这两种分类简称为基本类型（boolean, null, undefined, string, number, symbol）和object类型。首先，用一个example 演示参数传递的应用：var obj = {};obj.inner = 10;var num = 10;var str = Hello;var boo = true;var oth = null;var und = undefined;var sym = Symbol(foo);function passingobject(myobj){ myobj.inner = 1 + myobj.inner ; }function passingvalue(myvalue){ switch(typeof myvalue){ case number: myvalue = myvalue + 1; break; case string: myvalue = I am a new string now!; break; case boolean: myvalue= false; break; default: myvalue = Null, Undefined, or Symbol; } } console.log(before num = + num); // before num = 10 passingvalue(num); console.log(after num = + num); // after num = 10 console.log(before str = + str); // before str = Hello passingvalue(str); console.log(after str = + str); // after str = Hello console.log(before boo = + boo); // before boo = true passingvalue(boo); console.log(after boo = + boo); // after boo = false console.log(before oth = + oth); // before oth = null passingvalue(oth); console.log(after oth = + oth); // after oth = null console.log(before und = + und); // before und = undefined passingvalue(und); console.log(after und = + und); // after und = undefined console.log(sym); // Symbol(foo) passingvalue(sym); console.log(sym); // Symbol(foo) console.log(before obj.inner = + obj.inner); // before obj.inner = 10 passingobject(obj); // after obj.inner = 11 console.log(after obj.inner = + obj.inner);从example 1 的结果似乎可以总结出以下两条结论：1. 传递的数据类型为基本类型（number, string boolean, null, undefined, symbol），在参数传递过程中，函数内部对传递值的操作并不影响原始值。2. 传递的数据类型为object， 在参数传递过程中，函数内部对传递值的操作会导致原始值的改变。然而， 有没有其他特殊情况呢？有一种在stackoverflow讨论很火热的用法，跟结论二背道而行。example 2。例子引自：/questions/518000/is-javascript-a-pass-by-reference-or-pass-by-value-language 1 function changeStuff(a, b, c) 2 { 3 a = a * 10; 4 b.item = changed; 5 c = {item: changed}; 6 } 7 8 var num = 10; 9 va