This article discusses the preferred way to retrieve the last element of an Array in JavaScript. Tip 7 in this Useful JavaScript Hacks Article proposes the following method to get the last item in an array. syntax1.js var array = [1,2,3,4,5,6];console.log(array.slice(-1)[0]); /...
varcolors =newArray();//create an arrayvarcount = colors.push("red", "green");//push two itemsalert(count);//2count= colors.push("black");//push another item onalert(count);//3varitem = colors.pop();//get the last itemalert(item);//"black"alert(colors.length);//2 11、数组...
lastIndexOf() 方法可返回一个指定的元素在数组中最后出现的位置,从该字符串的后面向前查找。如果要检索的元素没有出现,则该方法返回 -1。该方法将从尾到头地检索数组中指定元素 item。开始检索的位置在数组的 start 处或数组的结尾(没有指定 start 参数时)。如果找到一个 item,则返回 item 从尾向前检索第一...
console.log(Object.entries(obj));//[ ['0', 'a'], ['1', 'b'], ['2', 'c'] ]//array like object with random key orderingconst anObj = { 100: 'a', 2: 'b', 7: 'c'}; console.log(Object.entries(anObj));//[ ['2', 'b'], ['7', 'c'], ['100', 'a'] ]//...
4. Last Elements of Array Write a JavaScript function to get the last element of an array. Passing the parameter 'n' will return the last 'n' elements of the array. Test Data: console.log(last([7, 9, 0, -2])); console.log(last([7, 9, 0, -2],3)); ...
first: element inserted at the beginning of array last: element inserted at the end of array. 代码语言:javascript 代码运行次数:0 运行 AI代码解释 functionappend(array,toAppend){constarrayCopy=array.slice();if(toAppend.first){arrayCopy.unshift(toAppend.first);}if(toAppend.last){arrayCopy.push...
Write a JavaScript function to get random items from an array. Visual Presentation: Sample Solution: JavaScript Code: // Function to return a random item from an arrayfunctionrandom_item(items){// Use Math.random() to generate a random number between 0 and 1,// multiply it by the length...
这使得这种检查只有在字符串没有那么长的情况下才是正确的。 现在我们只会在旧的代码中看到这个技巧,因为现代 JavaScript 提供了.includes方法。 str.lastIndexOf(substr [, pos]) 默认是str.length - 1开始,其余一样。 str.includes(substr [, pos]) 根据str中是否包含substr来返回true/false...
const castArray = (value) => (Array.isArray(value) ? value : [value]); 案例 castArray(1); // [1] castArray([1, 2, 3]); // [1, 2, 3] 1. 2. 3. 4. 5. 6. 7. 8. 9. 检查数组是否为空 js // `arr` is an array ...
.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arrinstanceofArray...