如何检查JSON中的字符串是否已使用Javascript更改

Question

I am trying to check if a string/date in a JSON file has changed but checking every second. How can I store this value and check the file for change or difference? Any help much appreciated.

// json example:
{
  "LastControlUpdateTime": "10:43:06.7147187"
}

var timeStamp;
function CompareTime() {
  $.getJSON(playlistJSONPath, function (data) {
    timeStamp = data.LastControlUpdateTime;

    if (timeStamp === data.LastControlUpdateTime) {
      console.log("same");
    } else {
      console.log("Diff");
    }
  });
}

CompareTime();
setInterval(CompareTime, 1000);

Answer 1

you are comparing the just assigned variable. this should do it.

var old_value;
function CompareTime() {
  $.getJSON(playlistJSONPath, function (data) {
    if (old_value == undefined) {
     old_value = data.LastControlUpdateTime;
    }
    else {
      if (data.LastControlUpdateTime != old_value) {
        console.log("value changed");
        old_value = data.LastControlUpdateTime;
      }
      else {
        console.log("value did not change");
      }
    }
  });
  setTimeout(function() { CompareTime();}, 1000)
}
CompareTime();