有人可以解释一下John Resig的pretty.js JavaScript是如何工作的吗？ [英] Can somebody explain how John Resig's pretty.js JavaScript works?

问题描述

http://ejohn.org/files/pretty.js

// Takes an ISO time and returns a string representing how
// long ago the date represents.
function prettyDate(time){
    var date = new Date((time || "").replace(/-/g,"/").replace(/[TZ]/g," ")),
        diff = (((new Date()).getTime() - date.getTime()) / 1000),
        day_diff = Math.floor(diff / 86400);

    if ( isNaN(day_diff) || day_diff < 0 || day_diff >= 31 )
        return;

    return day_diff == 0 && (
            diff < 60 && "just now" ||
            diff < 120 && "1 minute ago" ||
            diff < 3600 && Math.floor( diff / 60 ) + " minutes ago" ||
            diff < 7200 && "1 hour ago" ||
            diff < 86400 && Math.floor( diff / 3600 ) + " hours ago") ||
        day_diff == 1 && "Yesterday" ||
        day_diff < 7 && day_diff + " days ago" ||
        day_diff < 31 && Math.ceil( day_diff / 7 ) + " weeks ago";
}

// If jQuery is included in the page, adds a jQuery plugin to handle it as well
if ( typeof jQuery != "undefined" )
    jQuery.fn.prettyDate = function(){
        return this.each(function(){
            var date = prettyDate(this.title);
            if ( date )
                jQuery(this).text( date );
        });
    };

prettyDate（）方法到底是怎样的？返回一个字符串？这是你在JavaScript中可以做的那些奇怪事情中的另一个还是我只是遗漏了什么？

How exactly is the prettyDate() method returning a string? Is this another one of those 'strange' things you can do in JavaScript or am I just missing something?

编辑：我没有问他是如何返回一个值，我问他是如何返回一个字符串。

edit: I didn't ask how he's returning a value, I asked how he's returning a string.

return day_diff == 0&& （....）以我用过的任何语言返回一个布尔值。

return day_diff == 0 && (....) returns a boolean in any language I've ever used.

推荐答案

它在那里说： return ... 然后进入一个长嵌套列表，基本上是内联 ifs 。 ; - ）

It says right there: return ... and then goes into a long nested list of basically "inline ifs". ;-)

在Javascript中，布尔运算符返回其中一个操作数的值，而不仅仅是 true 或 false 。例如。 0 || 'foo'返回'foo'。该特性与操作员短路一起使用。 false&& true 不会评估 true 并立即返回 false ，因为整个表达式必须是 false 。

In Javascript, the boolean operators return the value of one of the operands, not just true or false. E.g. 0 || 'foo' returns 'foo'. This characteristic is used in conjunction with operator short-circuiting. false && true will not evaluate the true side and return false immediately, since the whole expression must be false.

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