计算字符串中每个字符的出现次数

本文介绍了计算字符串中每个字符的出现次数的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！ 问题描述

我想使用JavaScript计算给定字符串中每个字符的出现次数。

I want to count the number of occurrences of each character in a given string using JavaScript.

例如：

var str = "I want to count the number of occurances of each char in this string";

输出应为：

h = 4; e = 4; // and so on

我试图搜索Google，但没有找到任何答案。我希望实现这个;订单无关紧要。

I tried searching Google, but didn't find any answer. I want to achieve something like this; order doesn't matter.

推荐答案

这在JavaScript（或任何其他支持地图的语言）中非常简单：

This is really, really simple in JavaScript (or any other language that supports maps):

// The string var str = "I want to count the number of occurances of each char in this string"; // A map (in JavaScript, an object) for the character=>count mappings var counts = {}; // Misc vars var ch, index, len, count; // Loop through the string... for (index = 0, len = str.length; index < len; ++index) { // Get this character ch = str.charAt(index); // Not all engines support [] on strings // Get the count for it, if we have one; we'll get `undefined` if we // don't know this character yet count = counts[ch]; // If we have one, store that count plus one; if not, store one // We can rely on `count` being falsey if we haven't seen it before, // because we never store falsey numbers in the `counts` object. counts[ch] = count ? count + 1 : 1; }

现在计数已每个角色的属性;每个属性的值是计数。您可以输出以下内容：

Now counts has properties for each character; the value of each property is the count. You can output those like this:

for (ch in counts) { console.log(ch + " count: " + counts[ch]); }