按书上的样例，慢慢理解。
其实，JAVASCRIPT也应该可以写出正规点的，封装性好的代码。
<html>
<body>
<script type="text/javascript">
function findLivingCats() {
var livingCats = {"Spot": true,
"Noog": false,
"Biech": true,
"Cathy": false,
};
var mailArchive = ["died 06/12/2002 (mother Yellow Bess): Cathy Hobbles the 2nd, Cathy",
"born 20/09/2004 (mother Yellow Bess): Noog Hobbles the 2nd, Noog",
"born 12/11/2012 (mother Yellow Bess): Biech Hobbles the 2nd, Biech",
];
function startsWith(str, pattern) {
return str.slice(0, pattern.length) == pattern;
}
function catNames(paragraph) {
var colon = paragraph.indexOf(":");
console.log("colon: ", colon);
console.log("return: ", paragraph.slice(colon + 2).split(", "));
return paragraph.slice(colon + 2).split(", ");
}
function addToSet(set, values) {
for (var i = 0; i < values.length; i++)
set[values[i]] = true;
}
function removeFromSet(set, values) {
for (var i = 0; i < values.length; i++)
delete set[values[i]];
}
function handleParagraph(paragraph) {
if (startsWith(paragraph, "born")) {
addToSet(livingCats, catNames(paragraph));
}
else if(startsWith(paragraph, "died")) {
removeFromSet(livingCats, catNames(paragraph));
}
}
for (var mail = 0; mail < mailArchive.length; mail++) {
var paragraphs = mailArchive[mail].split("\n");
for (var i = 0; i < paragraphs.length; i++) {
handleParagraph(paragraphs[i]);
}
}
return livingCats;
}
var howMany = 0;
for (var cat in findLivingCats())
howMany++;
console.log("There are currently ", howMany, " cats alive.")
</script>
</body>
</html>