<!DOCTYPE html><html lang="en"><head> <meta charset="UTF-8"> <meta name="viewport" content="width=device-width, initial-scale=1.0"> <title>数组的查找、截取和拼接</title></head><body> <script> /* indexOf(searchValue[,fromIndex]) 查找目标字符串中，是否包含searchValue，如果包含，返回第一次出现的索引，如果不包含,返回-1 - searchValue 要查找的值 - fromIndex 查找的起始位置，如果不填，默认为0 如果大于或者等于length，则返回-1 如果说是一个负数（如果这个负数的绝对值超过length，则fromIndex为0），根据倒数来确认查找的位置 length + fromIndex */ var arr1 = ["E","a","b","c","a","d"]; console.log(arr1.indexOf("vv")); //打印：-1 console.log(arr1.indexOf("a",arr1.length)); //打印：-1 console.log(arr1.indexOf("a", -2)); //打印：4 console.log(arr1.indexOf("a", -50)); //打印：1 /* lastIndexOf(searchValue[,fromIndex]) 返回数组中指定的值最后一次出现的位置,如果不存在，则返回-1 fromIndex 搜索的起始位置，默认为length 如果大于或者等于length，则为length 如果是一个负数，则倒数找到对应的起始位置 length - fromIndex 如果负数的绝对值大于length,则返回 -1 */ console.log(arr1.lastIndexOf("a", arr1.length - 3)); //打印：1 console.log(arr1.lastIndexOf("a", 50)); //打印：4 console.log(arr1.lastIndexOf("vv")); //打印：-1 /* slice(begin,end) 用于截取数组中的内容，返回一个新数组 - begin - 如果不给，默认为0 - 截取的起始位置 - 如果值超过了length，就会返回一个空数组给你 - 如果是一个负数（负数的绝对值超过了length，就会默认从0开始截取），那就说明从倒数第begin开始截取 length + begin - end - 如果不给，默认到数组结尾 - 控制截取的结束位置 - 如果小于（从位置上来说）bengin，会得到一个空字符串 - 如果是负数（如果负数的绝对值超过了length，那么就会得到一个空字符串），那么就说明从倒数第end个结束。 - 如果超过了length，默认也只到数组的结尾位置 begin是包含在内的，end是不包含在截取范围内 */ var arr2 = ["a","b","c","d","e"]; console.log(arr2.slice(2)); //打印：["c","d","e"] console.log(arr2); //打印：["a","b","c","d","e"] console.log(arr2.slice(50)); //打印：[] console.log(arr2.slice(-2)); //打印：["d","e"] console.log(arr2.slice(-50)); //打印：["a","b","c","d","e"] console.log(arr2.slice(2,-1)); //打印：["c","d"] console.log(arr2.slice(0, -50)); //打印：[] console.log(arr2.slice(0, 50)); //打印：["a","b","c","d","e"] /* 深拷贝： 数据拷贝过来后，和原数组之间完全没有任何关系了 浅拷贝： 数据拷贝过来后，里面的第一层的基本类型是没有关联了，但是里面的复杂类型，依旧是有关联 赋址: 数据不管是基本类型，还是复杂类型，都和原来的是相关联的 */ //赋址 arr3 = arr2 arr3[0] = "123"; console.log(arr2,arr3); //打印：["123","b","c","d","e"] ["123","b","c","d","e"] var arr4 = ["a","b","c","d","e"]; var arr5 = arr4.slice(); arr5[0] = "123"; console.log(arr4,arr5); //打印：["a","b","c","d","e"] ["123","b","c","d","e"] var arr6 = [[1,2,3],"a"]; var arr7 = arr6.slice(); arr6[0][0] = "good"; console.log(arr6,arr7); //打印：[["good",2,3],"a"] [["good",2,3],"a"] /* concat 用于拼接两个或两个以上的数组，并返回一个新数组，并不会改变原有数组的值 */ var arr8 = ["I"]; var arr9 = ["love"]; var arr10 = ["you!"]; console.log(arr8.concat(arr9,arr10)); //打印：["I", "love", "you!"] /* join（sparator） 把数组拼接起来，以字符串的方式，进行返回，如果不给参数，默认以逗号进行间隔 sparator 决定以什么符号对数组的里面进行拼接 ** 如果数组是一个空数组的话，则会返回一个空字符串 */ var arr11 = ["I", "love", "you!"] console.log(arr11.join(" ")); //打印：I love you! var arr12 = [""]; console.log(arr12.join()); //打印：空 </script></body></html>