[英]How to get index element in array with two the same elements?
var array = ["ab", "cd", "ef", "ab", "gh"];
現在,我在位置0和3上具有"ab"
。我只希望在位置3上具有索引元素。我不希望在位置0上具有"ab"
。如何僅在位置3上獲得索引元素? 請幫忙。
第二種選擇:如果我有5個或更多元素怎么辦? 像這樣:
var array = ["ab", "cd", "ef", "ab", "gh", "ab", "kl", "ab", "ab"];
現在我想在位置5上添加元素?
讓我們嘗試一下:
var lastIndex = 0;
var checkValue = 'ab';
var array = ["ab", "cd", "ef", "ab", "gh"];
for(var i = 0; i < array.length; i++){
if(array[i] == checkValue) lastIndex = i;
};
簡單來說:
lastIndex
是包含最后一個匹配索引的變量; checkValue
是您要在數組中尋找的值; lastIndex
。 我有可以從數組中搜索任何內容的函數
var array = ["ab", "cd", "ef", "ab", "gh"]; function search(search, arr, callback) { for (var i = 0; i < arr.length; i++) { if (search === arr[i]) { callback(arr[i], i, arr); } } return -1; } search('ab', array, function(item, i) { alert(item + " : " + i); }); // or use this Array.prototype.search = function(search, callback) { for (var i = 0; i < this.length; i++) { if (search === this[i]) { callback(this[i], i, this); } } return -1; }; array.search('ab', function(item, i) { alert(item + " : " + i); });
我建議:
function findAll (needle, haystack) {
// we iterate over the supplied array using
// Array.prototype.map() to find those elements
// which are equal to the searched-for value
// (the needle in the haystack):
var indices = haystack.map(function (el, i) {
if (el === needle) {
// when a needle is found we return the
// index of that match:
return i;
}
// then we use Array.prototype.filter(Boolean)
// to retain only those values that are true,
// to filter out the otherwise undefined values
// returned by Array.prototype.map():
}).filter(Boolean);
// if the indices array is not empty (a zero
// length is evaluates to false/falsey) we
// return that array, otherwise we return -1
// to behave similarly to the indexOf() method:
return indices.length ? indices : -1;
}
var array = ["ab", "cd", "ef", "ab", "gh"],
needleAt = findAll('ab', array); // [0, 3]
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