如何在JavaScript中删除数组中的空元素?
是否有一种简单的方法,或者我需要循环并手动删除它们?
如何在JavaScript中删除数组中的空元素?
是否有一种简单的方法,或者我需要循环并手动删除它们?
当前回答
您应该使用filter获取不含空元素的数组。ES6示例
const array = [1, 32, 2, undefined, 3];
const newArray = array.filter(arr => arr);
其他回答
试试这个。将数组传递给它,它将返回并删除空元素*更新以解决Jason指出的错误
function removeEmptyElem(ary) {
for (var i = ary.length - 1; i >= 0; i--) {
if (ary[i] == undefined) {
ary.splice(i, 1);
}
}
return ary;
}
下面是一个使用变量行为和ES2015胖箭头表达式的示例:
Array.prototype.clean = function() {
var args = [].slice.call(arguments);
return this.filter(item => args.indexOf(item) === -1);
};
// Usage
var arr = ["", undefined, 3, "yes", undefined, undefined, ""];
arr.clean(undefined); // ["", 3, "yes", ""];
arr.clean(undefined, ""); // [3, "yes"];
“误用”。。。在(对象成员)循环中。=>循环体中仅显示真实值。
// --- Example ----------
var field = [];
field[0] = 'One';
field[1] = 1;
field[3] = true;
field[5] = 43.68;
field[7] = 'theLastElement';
// --- Example ----------
var originalLength;
// Store the length of the array.
originalLength = field.length;
for (var i in field) {
// Attach the truthy values upon the end of the array.
field.push(field[i]);
}
// Delete the original range within the array so that
// only the new elements are preserved.
field.splice(0, originalLength);
要移除孔,应使用
arr.filter(() => true)
arr.flat(0) // New in ES2019
对于删除孔、空和未定义:
arr.filter(x => x != null)
用于删除hole和falsy(null,undefined,0,-0,0n,NaN,“”,false,document.all)值:
arr.filter(x => x)
arr=[,null,(void 0),0,-0,0n,NaN,false,“”,42];console.log(arr.filter(()=>true));//[null,(void 0),0,-0,0n,NaN,false,“”,42]console.log(arr.filter(x=>x!=null));//[0,-0,0n,NaN,假,“”,42]console.log(arr.filter(x=>x));//[42]
注:
孔是一些没有元素的数组索引。
arr = [, ,];
console.log(arr[0], 0 in arr, arr.length); // undefined, false, 2; arr[0] is a hole
arr[42] = 42;
console.log(arr[10], 10 in arr, arr.length); // undefined, false, 43; arr[10] is a hole
arr1 = [1, 2, 3];
arr1[0] = (void 0);
console.log(arr1[0], 0 in arr1); // undefined, true; a[0] is undefined, not a hole
arr2 = [1, 2, 3];
delete arr2[0]; // NEVER do this please
console.log(arr2[0], 0 in arr2, arr2.length); // undefined, false; a[0] is a hole
上述所有方法都返回给定数组的副本,而不是就地修改它。
arr = [1, 3, null, 4];
filtered = arr.filter(x => x != null);
console.log(filtered); // [1, 3, 4]
console.log(arr); // [1, 3, null, 4]; not modified
您可能会发现,循环遍历数组并使用要从数组中保留的项构建新数组比按照建议进行循环和拼接更容易,因为在循环遍历时修改数组的长度可能会带来问题。
你可以这样做:
function removeFalsyElementsFromArray(someArray) {
var newArray = [];
for(var index = 0; index < someArray.length; index++) {
if(someArray[index]) {
newArray.push(someArray[index]);
}
}
return newArray;
}
实际上,这里有一个更通用的解决方案:
function removeElementsFromArray(someArray, filter) {
var newArray = [];
for(var index = 0; index < someArray.length; index++) {
if(filter(someArray[index]) == false) {
newArray.push(someArray[index]);
}
}
return newArray;
}
// then provide one or more filter functions that will
// filter out the elements based on some condition:
function isNullOrUndefined(item) {
return (item == null || typeof(item) == "undefined");
}
// then call the function like this:
var myArray = [1,2,,3,,3,,,,,,4,,4,,5,,6,,,,];
var results = removeElementsFromArray(myArray, isNullOrUndefined);
// results == [1,2,3,3,4,4,5,6]
你明白了——你可以有其他类型的过滤函数。可能比你需要的更多,但我感觉很慷慨…;)