Sometimes, you may need to validate the input values of a string variable and make sure that it is not empty or null. This can be useful for preventing errors, handling edge cases, or implementing conditional l
console.log("numberZero没值,为empty"); }else{ console.log("numberZero有值,不为empty") }if(!boolFalse) { console.log("boolFalse没值,为empty"); }else{ console.log("boolFalse有值,不为empty"); } 测试结果如下: ref:https://www.delftstack.com/howto/javascript/javascript-check-if-string...
Let's correct this by adding a constructor check. functiongoodEmptyCheck(value){Object.keys(value).length===0&&value.constructor===Object;// 👈 constructor check}goodEmptyCheck(newString());// false ✅goodEmptyCheck(newNumber());// false ✅goodEmptyCheck(newBoolean());// false ✅go...
function isEmpty(obj){ if(typeof obj == "undefined" || obj == null || obj == ""){ return true; }else{ return false; } } 1. 2. 3. 4. 5. 6. 7. 参考二: if (variable1 !== null || variable1 !== undefined || variable1 !== '') { var variable2 = variable1; } 1...
2. 简化 if true...else 对于不包含大逻辑的 if-else 条件,可以使用下面的快捷写法。我们可以简单地使用三元运算符来实现这种简化。 如果有嵌套的条件,可以这么做。 3. if 判断值是否存在 这是我们都在使用的一种常用的简便技巧,在这里仍然值得再提一下。
(If an empty array is not fine, add the minCount: 1 option.) For array items (when the key name ends with ".$"), if optional is true, then null values are valid. If array items are required, then any null items will fail the type check. If a key is required at a deeper ...
matcher(pwd); if (matcher.find()) { return "包含生日或者身份证"; } else { return "ok"; } } /*** * 描述: 密码规则 * * @param pwd 密码 * @return String */ public static String checkp(String pwd) { String str = "^(?![a-zA-Z]+$)(?![A-Z0-9]+$)(?![A-Z\\W_!@...
With the constructor, you can check if an object is aDate: Example (myDate.constructor=== Date); Try it Yourself » All Together typeof"John"// Returns "string" typeof("John"+"Doe")// Returns "string" typeof3.14// Returns "number" ...
Strings evaluate to false if an empty string '', otherwise true if ([0] && []) { // true // an array (even an empty one) is an object, objects will evaluate to true }15.3 Use shortcuts for booleans, but explicit comparisons for strings and numbers. // bad if (isValid === ...
3.6.2 函数转换(String to Number) JS提供了parseInt()和parseFloat()两个全局转换函数。前者把值转换成整数,后者把值转换成浮点数。只有对String类型调用这些方法,这两个函数才能正确运行,对其他类型返回的都是NaN。 (1)parseInt() 在转换之前,首先会分析该字符串,判断位置为0处的字符,判断它是否是一个有效数字...