var store = ['1','2','2','3','4'];
我想知道2出现在数组中最多。我该怎么做呢？
答案 0 :(得分：28)
我会做类似的事情：
var store = ['1','2','2','3','4'];
var frequency = {}; // array of frequency.
var max = 0; // holds the max frequency.
var result; // holds the max frequency element.
for(var v in store) {
frequency[store[v]]=(frequency[store[v]] || 0)+1; // increment frequency.
if(frequency[store[v]] > max) { // is this frequency > max so far ?
max = frequency[store[v]]; // update max.
result = store[v]; // update result.
}
}
答案 1 :(得分：4)
重点放在Array.prototype.forEach的解决方案以及如果在更多项目中共享最大计数而获得多个密钥的问题。
编辑：只有一个循环的提案。
var store = ['1', '2', '2', '3', '4', '5', '5'],
distribution = {},
max = 0,
result = [];
store.forEach(function (a) {
distribution[a] = (distribution[a] || 0) + 1;
if (distribution[a] > max) {
max = distribution[a];
result = [a];
return;
}
if (distribution[a] === max) {
result.push(a);
}
});
console.log('max: ' + max);
console.log('key/s with max count: ' + JSON.stringify(result));
console.log(distribution);
答案 2 :(得分：3)
arr.sort();
var max=0,result,freq = 0;
for(var i=0; i < arr.length; i++){
if(arr[i]===arr[i+1]){
freq++;
}
else {
freq=0;
}
if(freq>max){
result = arr[i];
max = freq;
}
}
return result;
答案 3 :(得分：2)
制作直方图，找到直方图中最大数字的关键字。
var hist = [];
for (var i = 0; i < store.length; i++) {
var n = store[i];
if (hist[n] === undefined) hist[n] = 0;
else hist[n]++;
}
var best_count = hist[store[0]];
var best = store[0];
for (var i = 0; i < store.length; i++) {
if (hist[store[i]] > best_count) {
best_count = hist[store[i]];
best = store[i];
}
}
alert(best + ' occurs the most at ' + best_count + ' occurrences');
这假设没有联系，或者你不关心选择哪个。
答案 4 :(得分：1)
如果数组已排序，则应该有效：
function popular(array) {
if (array.length == 0) return [null, 0];
var n = max = 1, maxNum = array[0], pv, cv;
for(var i = 0; i < array.length; i++, pv = array[i-1], cv = array[i]) {
if (pv == cv) {
if (++n >= max) {
max = n; maxNum = cv;
}
} else n = 1;
}
return [maxNum, max];
};
popular([1,2,2,3,4,9,9,9,9,1,1])
[9, 4]
popular([1,2,2,3,4,9,9,9,9,1,1,10,10,10,10,10])
[10, 5]
答案 5 :(得分：0)
当计数超过尚未计算的项目数时，此版本将退出查找。
无需对数组进行排序即可正常工作。
Array.prototype.most= function(){
var L= this.length, freq= [], unique= [],
tem, max= 1, index, count;
while(L>= max){
tem= this[--L];
if(unique.indexOf(tem)== -1){
unique.push(tem);
index= -1, count= 0;
while((index= this.indexOf(tem, index+1))!= -1){
++count;
}
if(count> max){
freq= [tem];
max= count;
}
else if(count== max) freq.push(tem);
}
}
return [freq, max];
}
//test
var A= ["apples","oranges","oranges","oranges","bananas",
"bananas","oranges","bananas"];
alert(A.most()) // [oranges,4]
A.push("bananas");
alert(A.most()) // [bananas,oranges,4]
答案 6 :(得分：0)
我这样解决了最常见的整数
function mostCommon(arr) {
// finds the first most common integer, doesn't account for 2 equally common integers (a tie)
freq = [];
// set all frequency counts to 0
for(i = 0; i < arr[arr.length-1]; i++) {
freq[i] = 0;
}
// use index in freq to represent the number, and the value at the index represent the frequency count
for(i = 0; i < arr.length; i++) {
freq[arr[i]]++;
}
// find biggest number's index, that's the most frequent integer
mostCommon = freq[0];
for(i = 0; i < freq.length; i++) {
if(freq[i] > mostCommon) {
mostCommon = i;
}
}
return mostCommon;
}
答案 7 :(得分：0)
这是我的解决方案。
var max_frequent_elements = function(arr){
var a = [], b = [], prev;
arr.sort();
for ( var i = 0; i < arr.length; i++ ) {
if ( arr[i] !== prev ) {
a.push(arr[i]);
b.push(1);
} else {
b[b.length-1]++;
}
prev = arr[i];
}
var max = b[0]
for(var p=1;p<b.length;p++){
if(b[p]>max)max=b[p]
}
var indices = []
for(var q=0;q<a.length;q++){
if(b[q]==max){indices.push(a[q])}
}
return indices;
};
答案 8 :(得分：-1)
如果数组包含字符串，请尝试此解决方案
function GetMaxFrequency (array) {
var store = array;
var frequency = []; // array of frequency.
var result; // holds the max frequency element.
for(var v in store) {
var target = store[v];
var numOccurences = $.grep(store, function (elem) {
return elem === target;
}).length;
frequency.push(numOccurences);
}
maxValue = Math.max.apply(this, frequency);
result = store[$.inArray(maxValue,frequency)];
return result;
}
var store = ['ff','cc','cc','ff','ff','ff','ff','ff','ff','yahya','yahya','cc','yahya'];
alert(GetMaxFrequency(store));
答案 9 :(得分：-1)
一个相当简短的解决方案。
function mostCommon(list) {
var keyCounts = {};
var topCount = 0;
var topKey = {};
list.forEach(function(item, val) {
keyCounts[item] = keyCounts[item] + 1 || 1;
if (keyCounts[item] > topCount) {
topKey = item;
topCount = keyCounts[item];
}
});
return topKey;
}
document.write(mostCommon(['AA', 'AA', 'AB', 'AC']))
答案 10 :(得分：-1)
此解决方案返回数组中出现最多数字的数组，以防多个数字出现在＆＃34; max＆＃34;次。
function mode(numbers) {
var counterObj = {};
var max = 0;
var result = [];
for(let num in numbers) {
counterObj[numbers[num]] = (counterObj[numbers[num]] || 0) + 1;
if(counterObj[numbers[num]] >= max) {
max = counterObj[numbers[num]];
}
}
for (let num in counterObj) {
if(counterObj[num] == max) {
result.push(parseInt(num));
}
}
return result;
}
答案 11 :(得分：-1)
上述所有解决方案都是迭代的。
这是一个ES6功能无突变版本：
Array.prototype.mostRepresented = function() {
const indexedElements = this.reduce((result, element) => {
return result.map(el => {
return {
value: el.value,
count: el.count + (el.value === element ? 1 : 0),
};
}).concat(result.some(el => el.value === element) ? [] : {value: element, count: 1});
}, []);
return (indexedElements.slice(1).reduce(
(result, indexedElement) => (indexedElement.count > result.count ? indexedElement : result),
indexedElements[0]) || {}).value;
};
它可以在性能成为瓶颈的特定情况下进行优化，但它具有使用任何类型数组元素的巨大优势。
最后一行可以替换为：
return (indexedElements.maxBy(el => el.count) || {}).value;
使用：
Array.prototype.maxBy = function(fn) {
return this.slice(1).reduce((result, element) => (fn(element) > fn(result) ? element : result), this[0]);
};
为了清晰起见