javascript数组特性

来源：互联网发布：apache mpm winnt 编辑：程序博客网时间：2024/06/08 00:11
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN""http://www.w3.org/TR/html4/loose.dtd"><html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=utf-8" /><script type="text/javascript" charset="UTF-8">/** *  indexof()  和 lastIndexOf()  获取某个值的索引 */var arr = [1,2,3,4,5,4,3,2,1];var v1 = arr.indexOf(4);//从前往后该值的第一个下标位置console.log(v1);//3var v2 = arr.lastIndexOf(2);console.log(v2);//7/** * every() :执行传入的函数，判断每个元素是否满足条件 ，全部满足才能返回true，否则为false */var arr1 = [1,2,3,4,5,6,7,8,9];var result1 = arr1.every(function(item,index,array){return item>2;})console.log(result1);//false/** * filter() ：执行传入的函数，过滤掉不满足函数的元素，返回满足函数的元素组成的数组 */var arr2 = [1,2,3,4,5,6,7,8,9];var result2 = arr2.filter(function(item,index,array){return item>3;});console.log(result2);// [4, 5, 6, 7, 8, 9]/** * foreach()：遍历数组的每个元素，执行传入的函数 */var arr3 = [1,2,3,4,5,6];arr3.forEach(function(item,index,array){alert(item+'__'+index);});/** * map()::执行传入的函数，对每个元素都进行了函数执行，返回一个数组 */var arr4 = [1,2,3,4,5];var result4 = arr4.map(function(item,index,array){return item*2;});console.log(result4); // [2, 4, 6, 8, 10]/** * some() ：对数组的每个元素执行函数，有一个满足函数的就返回true,否则返回false */var arr5 = [1,2,3,4,5];var result5 = arr5.some(function(item,index,array){return item>=5;});console.log(result5);</script></head><body></body></html>
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