字典的實現
// 字典類
function Dictionary () {
this.add = add;
this.dataStore = new Array();
this.find = find;
this.remove = remove;
this.showAll = showAll;
this.count = count;
this.clear = clear;
}
function add (key, value) {
this.dataStore[key] = value;
}
function find (key) {
return this.dataStore[key];
}
function remove (key) {
delete this.dataStore[key];
}
function showAll () {
let datakeys = Array.prototype.slice.call(Object.keys(this.dataStore));
for (let key in datakeys.sort()) {
console.log(`${datakeys[key]} -> ${this.dataStore[datakeys[key]]}`);
}
}
// 計數
function count () {
let n = 0;
for (let key in Object.keys(this.dataStore)) {
++n;
}
return n;
}
// 清空
function clear () {
Object.keys(this.dataStore).forEach((key) => {
delete this.dataStore[key];
}, this);
}
練習
使用Dictionary類寫一個程序，該程序用來存儲一段文本中各個單詞出現的次數。該程序顯示每個單詞出現的次數，但每個單詞只顯示一次。比如下面一段話“the brown fox jumped over the blue fox”，程序的輸出應為：
- the: 2
- brown: 1
- fox: 2
- jumped: 1
- over: 1
- blue: 1
function showWordCount (word) {
let d = new Dictionary();
let words = word.split(' ');
for (let i = 0, max = words.length; i < max; ++i) {
// 首次出現
if (typeof d.find(words[i]) === 'undefined') {
d.add(words[i], 1);
} else {
++d.dataStore[words[i]];
}
}
Object.keys(d.dataStore).forEach((key) => {
console.log(`${key}: ${d.find(key)}`);
}, this);
}
// 示例
showWordCount('the brown fox jumped over the blue fox');
