javascript - Result of loop is undefined -

function argument stored in such format

["2015-07-05 00:30", 59] ... ["2015-07-05 01:00", 62] 

function generatecsv(timeandvalue) {     object = {}     var 0 = 0;     for(i = 0; < timeandvalue.length; i++){         var value = timeandvalue[i]         var days = moment(value[0]).format('yyyy-mm-dd');         obj[days] += value[1] + ', '     } } 

in loop object takes days parameter , amount of value spent on day. 2015-07-05:

"2015-07-05: "undefined59, 62, 65...

2015-07-06: "undefined61, 61, 60..."

every parameter value beginning "undefined". how can loop parameters wouldn't begin "undefined"?

replace

obj[days] += value[1] + ', ' 

with

if (obj[days]===undefined) obj[days] = '';  obj[days] += value[1] + ', ' 

so don't add string undefined.

but instead of adding ", " after every values, build array in loop:

if (obj[days]===undefined) obj[days] = [];  obj[days].push(value[1]) 

and use join @ end avoid trailing comma (and on general principle string building should deferred rendering time).

be careful variable declarations: object might ok, assuming it's defined in outside scope, missing declaration of i dangerous, it's probable it's not i in application.

edit: seen james, have typo, it's either "object" or "obj".