在 Javascript 中循环数组时检测值何时发生变化？

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Answer 1

var events = [/* as in the question */];
var groupedEvents = {};

for (var i = 0; i < events.length; ++i) {
    var time = events[i].section;
    var action = events[i].title;

    if (!groupedEvents.hasOwnProperty(time)) {
         groupedEvents[time] = [];
    }
    groupedEvents[time].push(action);
}

现在groupedEvents包含：

{
     "An Hour before Dinner": ["Cook peas", "Take pie out"],
     "As guests arrive": ["Mix Drinks"],
     "Just before dessert": ["Reheat at 325 about 20 minutes.", "Cut and serve."]
}

Answer 2

这应该可以解决问题：

var arr = [
    {section:"An Hour before Dinner", title:"Cook peas"},
    {section:"An Hour before Dinner", title:"Take pie out"},
    {section:"As guests arrive", title:"Mix drinks"},
    {section:"Just Before Dessert", title:"Reheat at 325 about 20 minutes."},
    {section:"Just Before Dessert", title:"Cut and serve."}
];
var s = null;

var html = "";
for (var i = 0, l = arr.length; i<l; i++) {
    var r = arr[i];
    if (r.section != s) {
        // New section
        s = r.section;
        html += "<h1>"+s+"</h1>"
    } else {
        // Continue old section
    }
    html += "<p>"+r.title+"</p>";
}

var div = document.createElement('div');
div.innerHTML = html;
document.body.appendChild(div);

Answer 3

假设它们已正确排序，并且位于数组“arr”中：

var pre = '';
for (var i = 0; i < arr.length; i++) {
   if (arr[i].section != pre) displayHeading(arr[i]);
   pre = arr[i];
   displayContent(arr[i]);
}