使用contains函数确定指定对象是否是Array对象中的元素。 在Mozilla Firefox 中,如果数组中的项已设置为undefined,则调用item 设置为undefined 的contains函数将返回true。同样的情况下,在所有其他浏览器中,函数都返回false。
regs.push(new Array("item_1","^[\\s\\S]+$","item_1Span","法人代表不能为空","填写正确",true)); regs.push(new Array("item_2","^[\\s\\S]+$","item_2Span","开户银行不能为空","填写正确",true)); regs.push(new Array("item_3","^[\\s\\S]+$","item_3Span","帐号...
使用filter(注意:array.filter(e=>e==x).length > 0等效于array.some(e=>e==x)但some更有效) function contains(arr, val) { return arr.filter((item)=> { return item == val }).length > 0; } 1. 2. 3. 方式三:array.indexOf array.indexOf此方法判断数组中是否存在某个值,如果存在返回数...
It’s really nice to know whether or not an item is contained within your array. Well you can write a function that takes the array and the item you’re checking for, but it’s much cleaner to add the contains( item ) method to the Array object. Extending JavaScript Arrays /** * A...
functioncontains(arr, val){returnarr.filter((item)=>{returnitem == val }).length >0;} 方式三:array.indexOf array.indexOf此方法判断数组中是否存在某个值,如果存在返回数组元素的下标,否则返回-1。 [1, 2, 3].indexOf(1);//0["foo","fl...
这段代码通过prototype定义了数组方法,这样就可以在任意数组调用contains方法 1 2 3 4 5 6 7 8 9 10 11 12 /** * Array.prototype.[method name] allows you to define/overwrite an objects method * needle is the item you are searching for ...
functionmyFunction(value, index, array) { returnvalue *2; } Try it Yourself » Note that the function takes 3 arguments: The item value The item index The array itself When a callback function uses only the value parameter, the index and array parameters can be omitted: ...
const = contains = (() => Array.prototype.includes ? (arr, value) => arr.includes(value) : (arr, value) => arr.some(el => el ===value))(); contains(['foo', 'bar'], 'baz'); // false 另外,Map和Set数据结构有一个has方法,需要注意includes区分。 代码语言:javascript 代码运行次数...
An array can hold many values under a single name, and you can access the values by referring to an index number. Creating an Array Using an array literal is the easiest way to create a JavaScript Array. Syntax: constarray_name= [item1,item2, ...]; ...
console.log([]instanceofArray);//truefunctionStudent(){}//定义构造函数vartom=newStudent();//实例化一个Student对象console.log(tominstanceofStudent);//trueconsole.log(tominstanceofObject);//trueconsole.log(tominstanceofNumber);//false 输出结果如图1-3所示。