// program to check if an object is an array function checkObject(arr) { // check if arr is array const result = Array.isArray(arr); if(result) { console.log(`[${arr}] is an array.`); } else { console.log(`${arr
判断时使用Object.prototype.toString.call( list )==='[object Array]'或者Object.prototype.toString.call( list )=='[object Array]',==或者===一样的效果。 测试3: 如果使用jquery,可以使用$.isArray(obj)的方法,如下: vara = ["A", "AA", "AAA"];if($.isArray(a)) { console.log("a is ...
if($.isArray(arrayList))console.log('数组'); 别的console.log('不是数组'); 仅供参考要确定一个对象是否是一个数组,jQuery 在内部使用 Object.prototype.toString.call 方法。 您还可以使用现代浏览器来: Array.isArray(arrayList); Array.is Chrome 5、Firefox 4.0、Internet Explorer 9、Opera 10.5 和 Sa...
通过测试,使用如:obj instanceof Object的形式,只能是判断两种类型Object和Array,其中Boolean、Number、String可以判断,但是会返回false,如上面i和b变量;如果判断为null或者undefind会报Uncaught TypeError: Right-hand side of 'instanceof' is not an object这样的错误。 测试5: 直接通过Array.isArray(obj),javascri...
Checks if value is classified as an Array object. constarray=['🍝','🍜','🍲'];constnotArray='not array';_.isArray(array);// true_.isArray(notArray);// false Underscore Returns true if object is an Array. constarray=['🍝','🍜','🍲'];constnotArray='not array';_.isArr...
Iterate the array used for the normal loop Check each element for true value using the loop if found, return true and break from the loop if not found, return a false value // function return if an element is found in the array, else falsefunctioncheckTrueExistsArray(array) {for(vark=...
Add value if not exists Loop through the array to check whether a particular username value already exists and if it does do nothing, but if it doesn’t add a new object to the array. const arr = [{ id: 1, username: 'fred' }, { id: 2, username: 'bill' }, { id: 3,...
If you don't want it to throw aTypeError, you can add an extra check: letvalue;value// 👈 null and undefined check&&Object.keys(value).length===0&&value.constructor===Object;value=null;// nullvalue=undefined;// undefined Perfect, no error is thrown 😁 ...
. Every Array object has alengthproperty whose value is always a nonnegative integer less than 2...
function checkData() { if (document.form1.threeChar.value.length == 3) { return true; } else { alert("Enter exactly three characters. " + document.form1.threeChar.value + " is not valid."); return false; } } 「switch 语句节」switch 语句允许一个程序求一个表达式的值并且尝试去匹配表...