JS interesting eval optimization input validation example code_javascript skills

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//eval is to calculate the string [you can put any js The value in the code is
//1,
var str1='12 3';
eval(str1);//15

//2、
var str2='[1,2,3]';
eval(str2[0]);//1

//3.
eval('alert("abc")');//Pop up abc

//4.
var str="function show(){alert('love you');}";
eval(str);
show();

//5. eval--->json string

1. If the above user name and email verification input are blank, the traditional method is

Copy code The code is as follows:

var flag = true;
if (document. getElementById("txtName").value == "") {
                                                                                                                                                                  xtEmail").value = = "") {
                                                                                                                                                                                                ; 🎜>-->But how? There are many fields that need to be verified, there will be a lot of ifs, and they are not elegant at all

2. To calm down, let’s take a look at html





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The code is as follows:

Username:

Email:< br /> 2.1 Look at the following code

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The code is as follows:

function validateForm() {

var nameV = form1.name.value() alert(nameV);//If we enter "short-haired beauty" in the text box, it will definitely be "short-haired beauty" that pops up >             nameV=eval('form1.name.value()');                       alert(nameV);

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The code is as follows:

function FormField(fieldName, fieldDesc) {//Encapsulate the changer attribute fields and descriptions
this.fieldName = fieldName;
this.fieldDesc = fieldDesc;
}
String.prototype.MyTrim = function () {//Remove leading and trailing spaces
                                                                                                                                                                                                     . >
var oUl = document.getElementById("ulError");
oUl.innerHTML = "";
var list = new Array
(
//You only need to verify that it is empty in the future Just add an object to the array
new FormField("name", "username"),
new FormField("email", "mail")
var flag = true; eval operation
if (fv == null ||!fv.MyTrim()) {
  fieldDesc " Cannot be empty liError.innerHTML =list[i].fieldDesc " Cannot be empty";
                                                                                                                                             🎜>