javascript - Return -1 if JSON Array is NULL works only in some data -

i wanted to:

• return -1 if data(array) null or empty
• if data not null , if array has rain_value property wanted 2nd index value of array based on length

below snippet of code:

success: function (data) {         //console.log(data);     $.map(data, function (e) {         var max = -1;         var dev_id = e.dev_id;         var data = e.data;         var r;         if (data) {             (var j = 0; j < data.length; j++) {                 r = parsefloat(data[j].rain_value) || 0;                 arr[j] = parsefloat(r);             }         }         if (arr.length) {             max = arr[1] * 4;             //max = math.max.apply(math, arr) * 4;         }          (var k = 0; k < len; k++) {             var jsonobj_device_id = jsonobj.features[k].properties.device_id;             if (jsonobj_device_id == dev_id) {                 var namer = "rain_intensity";                 var rainvalue = max;                 jsonobj.features[k].properties[namer] = rainvalue;             }         }         console.log(dev_id + " " + max)     }); } 

i can't seem figure out why works in data. here's fiddle. thanks!

you assigning empty array value variable arr outside loop, not within loop. means have data , array populated every following iteration have array values. need clear every time, or declare in loop...

success: function (data) {         //console.log(data);     $.map(data, function (e) {         var max = -1;         var dev_id = e.dev_id;         var data = e.data;         var r;         arr = [];   // <---- clear array here         if (data) {             (var j = 0; j < data.length; j++) {                 r = parsefloat(data[j].rain_value) || 0;                 arr[j] = parsefloat(r);             }         }         if (arr.length) {             max = arr[1] * 4;             //max = math.max.apply(math, arr) * 4;         }          (var k = 0; k < len; k++) {             var jsonobj_device_id = jsonobj.features[k].properties.device_id;             if (jsonobj_device_id == dev_id) {                 var namer = "rain_intensity";                 var rainvalue = max;                 jsonobj.features[k].properties[namer] = rainvalue;             }         }         console.log(dev_id + " " + max)     }); } 

working jsfiddle link