if ( val == null ) { val = ""; } What does this code do? And why is it a common exception to the triple equals rule? Let's take a look at an example where it might be useful.var ethos = { achilles: "glory", aeneas: "duty", hades: null // Beyond human understanding };...
If Type(x) is Boolean, return true if x and y are both true or both false. Otherwise, return false. Return true if x and y refer to the same object or if they refer to objects joined to each other (see 13.1.2). Otherwise, return false. If x is null and y is undefined, retur...
null <= 0, null == 0 undefined <= null, undefined == null '' <= 0, '' == 0, if ('') ' ' <= 0, ' ' == 0, if (' ') '0' <= 0, '0' == 0 NaN <= 0, NaN == 0, NaN >= 0 '2' <= true, '2' == true '0' <= false, '0' == false, if ('0') ...
Object.is) { Object.defineProperty(Object, "is", { value: function (x, y) { // SameValue algorithm if (x === y) { // return true if x and y are not 0, OR // if x and y are both 0 of the same sign. // This checks for cases 1 and 2 above. re...
1. 空值测试：空值（null、undefined） ≠ 非空值（所有不是null、undefined的值）典型代码： if (x ...
if (textBoxValue.trim() === "") { // 文本框为空 } else { // 文本框不为空 } 执行相应的操作:根据文本框是否为空,可以执行相应的操作,例如显示错误消息、禁用提交按钮等。 完善且全面的答案如下: JavaScript是一种广泛应用于前端开发的脚本语言,可以通过它来检查文本框是否为空。通过获取文本框的值,...
currentInput)return;// 如果已有运算符且未输入新数字,则不处理if(firstValue===null){firstValue=parseFloat(currentInput);formulaDisplay+=`${value}`;}else{// 计算并更新显示constsecondValue=parseFloat(currentInput);firstValue=operate(operator,firstValue,secondValue);formulaDisplay=`${firstValue}${value...
1. 空值测试：空值（null、undefined） ≠ 非空值（所有不是null、undefined的值）典型代码： if (x ...
function Object.prototype.equals(obj){ if(this == obj)return true; if(typeof(obj)=="undefined"||obj==null||typeof(obj)!="object")return false; var length = 0; var length1=0; for(var ele in this) length++;for(var ele in obj) length1++; ...
FileItem rangeFile = null; Iterator fileItr = files.iterator(); while (fileItr.hasNext()) { rangeFile = (FileItem) fileItr.next(); if(StringUtils.equals( rangeFile.getFieldName(),"pathSvr")) { pathSvr = rangeFile.getString(); ...