javascript - 如何将值输入与新输入 javascript 进行比较

Question

我想知道如何在 javascript 中执行以下操作：我在表单上有一个字段，其值（浮点数）存储在数据库中，我们称之为初始值。每次用户改变这个字段的值，我们称它为新的，我想在提交表单之前比较新值和初始值？我怎样才能做到这一点？

干杯

Answer 1

Since no HTML was given, lets assume your input has id of txtInput

var initial = "someDBVal";

//assigning a change handler to your input
document.getElementById("txtInput").onchange = function() {
    var newx = document.getElementById("txtInput").value;

    if (newx == initial) {
        alert("they match");
    } else {
        alert("no match");
    }
}

Demo: http://jsfiddle.net/tymeJV/Bdpxd/

Answer 2

var initial = 0.123;
document.getElementById("theinput").onchange = function() {
    var _new = document.getElementById("theinput").value;

    if (parseFloat(_new) == parseFloat(initial)) {
        console.log("equal");
    } else {
        console.log("not equal");
    }
}