循环通过JSON数据中的最小值和最大值（无jQuery）

Question

在下面的：

function processResponse(response){
    var myObj = JSON.parse(response); // convert string to object
    var weighInData = myObj["WEIGH-INS"];
    var dataRows = document.getElementById("data-rows");
    dataRows.innerHTML = "";

    for (var obj in weighInData) {
        if (weighInData[obj].user === selUser) { // *
            var weights = JSON.parse("[" + weighInData[obj].weight + "]"); // convert to object
            var row = "<tr>" +
                            "<td class=\"date\">" + weighInData[obj].date + " </td>" +
                            "<td class=\"value\">" + weighInData[obj].weight + "</td>" +
                        "</tr>";
            var userDisplayEl = document.getElementById("user-display");
            userDisplayEl.innerHTML = weighInData[obj].user;
            output.innerHTML += row;
        } // if ... === selUser
    } // for var obj in weighInData
} // processResponse

• if（weighInData [obj] .user === selUser）{...返回以下内容（使用示例Ron）：

  对象{user =“ Ron”，date =“ 2014-08-01”，weight =“ 192”}

  对象{user =“ Ron”，date =“ 2014-08-02”，weight =“ 195”}

  对象{user =“ Ron”，date =“ 2014-08-03”，weight =“ 198”} ...等等。

...所以我目前的问题是它所属的位置：var peakWeight = Math.max.apply（Math，weights）; console.log（“ peakWeight：” + peakWeight）;

因为我只关注匹配用户的权重值，所以我认为它必须在'if（weighInData [obj] .user === selUser）{...'循环内和循环外，包括selUser中的for循环）都无法获得所需的结果。 实际上，即使数学函数未在“权重”中的每个值上运行（即不在循环内），而是仅在循环外运行，结果仍为不正确的值。

非常感谢您的见解，

svs

Answer 1

这是一个非常简单的示例，您可以调整以适合您的目的：

// create this array outside of for loop so it already exists
var arr = []; 

// test data
var a = { user:"Ron", date:"2014-08-01", weight:"192"};
var b = { user:"Ron", date:"2014-08-02", weight:"195"};
var c = { user:"Ron", date:"2014-08-03", weight:"198"};        

// within for loop, you should only need to push once (per loop)
arr.push( a.weight );
arr.push( b.weight );
arr.push( c.weight );

// after the loop ends, display loop, get max and display
alert(arr);
var peakWeight = Math.max.apply(null, arr);
var minWeight = Math.min.apply(null, arr);
alert("Max: " + peakWeight + " -- Min: " + minWeight);

http://jsfiddle.net/biz79/sb7zayze/

如果我要编辑您的代码，则可能会执行以下操作：

function processResponse(response){
    var myObj = JSON.parse(response); // convert string to object
    var weighInData = myObj["WEIGH-INS"];
    var dataRows = document.getElementById("data-rows");
    dataRows.innerHTML = "";

    // ADDED: create array
    var arr = [];  

    for (var obj in weighInData) {
        if (weighInData[obj].user === selUser) { // *
            var weights = JSON.parse("[" + weighInData[obj].weight + "]"); // convert to object

            // ADDED:  add to array
            arr.push(weights);

            var row = "<tr>" +
                            "<td class=\"date\">" + weighInData[obj].date + " </td>" +
                            "<td class=\"value\">" + weighInData[obj].weight + "</td>" +
                        "</tr>";
            var userDisplayEl = document.getElementById("user-display");
            userDisplayEl.innerHTML = weighInData[obj].user;
            output.innerHTML += row;
        } // if ... === selUser
    } // for var obj in weighInData

  // ADDED: after the loop ends, display loop, get max/min and display
  alert(arr);
  var peakWeight = Math.max.apply(null, arr);
  var minWeight = Math.min.apply(null, arr);
  alert("Max: " + peakWeight + " -- Min: " + minWeight);       

} // processResponse