Javascript 更新函数内的全局对象

Question

我看到我的全局变量(一个对象)正在函数内部被修改。

下面是我创建的示例:

var globalVarForTest = ["dfbsdfbsdfb", "sfgb", "gtsgt", "ttt"];

function testingError() {

  console.log("BEFORE")
  console.log(globalVarForTest);
  for (var i = 0; i < globalVarForTest.length; i++) {
    console.log(globalVarForTest[i]);
  }


  //Modifying Local Variable
  var localVarforTest = globalVarForTest;
  for (var i = 0; i < localVarforTest.length; i++) {
    localVarforTest[i] = localVarforTest[i].length;
  }




  console.log("AFTER")
  console.log(globalVarForTest);
  for (var i = 0; i < globalVarForTest.length; i++) {
    console.log(globalVarForTest[i]);
  }

}

testingError();

该函数打印全局变量的 BEFORE 和 AFTER 不同值。

如何将函数内部的局部变量设置为等于全局数组，使得全局数组在函数中不被修改？

Answer 1

你必须clone it without reference .

var globalVarForTest = ["dfbsdfbsdfb","sfgb","gtsgt","ttt"];

var temp = globalVarForTest.slice(0);

console.log(temp);
temp.push('temp');
console.log(temp);
console.log(globalVarForTest);