它还检查数组是否为“undefined”或为“null”。 使用array.length属性检查数组是否为空;此属性返回数组中的元素数量。如果这个数大于0,它的值为true。 数组的isArray()方法和length属性可与(&&)操作符一起使用,以确定数组是否存在且是否为空。 语法: Array.isArray(emptyArray) && emptyArray.length 例: <!DOCT...
goodEmptyCheck(newArray());//false?goodEmptyCheck(newRegExp());//false?goodEmptyCheck(newFunction());//false?goodEmptyCheck(newDate());//false?这样一来，避免了其他情况的影响 其他特殊值的判断，null,undefined当碰到null,undefined时，会抛出错误 //TypeError:Cannotcovertundefinedornullot...
constiframe=document.createElement("iframe");document.body.appendChild(iframe);constxArray=window.frames[window.frames.length-1].Array;constarr=newxArray(1,2,3);// [1, 2, 3]// 正确检查 ArrayArray.isArray(arr);// true// arr 的原型是 xArray.prototype,它是一个不同于 Array.prototype 的对象...
//而 Array(5) 创建一个长度为7的空数组,这是指一个有5个空位(empty)的数组,而不是由7个undefined组成的数组)。 Array(5); // [ , , , , ] Array(1, 2, 3); // [1, 2, 3] // Array.isArray 用于确定传递的值是否是一个 Array Array.isArray([1, 2, 3]); // true Array.isArray...
function checkArray() { let emptyArray = []; let nonExistantArray = undefined; let fineArray = [1, 2, 3, 4, 5]; if(Array.isArray(emptyArray) && emptyArray.length) output = true; else output = false; document.querySelector('.output-empty').textContent = output; ...
JavaScript中有6种数据类型,其中有五种简单的数据类型:Undefined、Null、布尔、数值和字符串,一种复杂数据类型:Object。 对象(Object):各种值组成的集合 (1)对象(object) 如:{name:"zhangsan",age:"18"} (2)数组(array) 如:[1,2,3] (3)函数(function)如:function test() {} 1. 2. 3. 4. 3.5.1...
Array.isArray(t)?t.map(X):(t=X(t))in r?[t]:t.match(P)||[]).length;while(n--)delete r[t[n]]}(void 0===t||S.isEmptyObject(r))&&(e.nodeType?e[this.expando]=void 0:delete e[this.expando])}},hasData:function(e){var t=e[this.expando];return void 0!==t&&!S.is...
If an empty array is passed to this property then none of the sublayers from the service are displayed in the layer. All sublayers are referenced in the order in which they are drawn in the view (bottom to top). They may be added, removed, or reordered using the Collection methods. ...
first=10&second=6.5&last=someValue'// If params order is important for you, better use pairs array (objects are sometimes reordered in Javascript)varparams2=[['first',10],['second',6.5],['last','someValue']];_q2.buildQuery(params2);// => '?first=10&second=6.5&last=someValue'//...
The ground may not be set to null or undefined, it is guaranteed to always contain an instance of type Ground. The elevation can be removed from the ground by setting the ground property to a new empty Ground instance or by removing all the ground layers. See also ElevationLayer Ground Ex...