javascript - Underscore extend an object -

i want extend object add attribute:

var days = [{day:'monday'},{day:'tuesday'}];     _.extend(days,{day:'monday'},{name:'peter'});  // days not extended console.log(days); // want have result // [{day:'monday',name:'peter'},{day:'tuesday'}] 

the goal able update or insert depending of criteria, want find 'monday' , extend, 'tuesday' , extend , on ... if find 'monday' again want remove name attribute , replace new criteria

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update

this solution t.j crowder, update object if search new criteria same day :

var days = [{day:'monday'},{day:'tuesday'}]; var day = _.find(days, function(day) {   return day.day == 'monday'; });  if (day) {   _.extend(day,{day:'monday'},{name:'peter'}); }  console.log(days); 

this output (here search 'monday' , insert peter, same ronald, , search 'monday' again , update name sandy) : code update insert new day 'monday' @ last of object

///// initial object ({     'day':'monday' },{     'day':'tuesday' }) ///// search 'monday' , add {name : 'peter'} ({     'name':'peter',     'day':'monday' },{     'day':'tuesday' },{     'day':'monday' })   //// search 'monday' again , update {name : 'sandy'} ({     'name':'sandy',     'day':'monday' },{     'day':'tuesday' },{     'day':'monday' },{     'day':'monday' }) 

so question why extends {day:'monday'} each update ?

thank you

it does add properties array, they're not being shown, , they're not being added want them because aren't using _.extend in way would. you're extending array; want extend array's first entry. here's what want, note [0]:

var days = [{day:'monday'},{day:'tuesday'}];  _.extend(days[0],{day:'monday'},{name:'peter'});  // note -----^^^    console.log(days);

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of course, assumes know index of day: 'monday' 0. if don't, you'll need find day first, perhaps using _.find:

var days = [{day:'monday'},{day:'tuesday'}];  var day = _.find(days, function(day) {    return day.day == 'monday';  });  if (day) {    _.extend(day,{day:'monday'},{name:'peter'});  }    console.log(days);

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in edit question, said code above keeps adding {day: 'monday'} array. doesn't. let's put in function , repeatedly call function:

function extendday(dayname, properties) {    var day = _.find(days, function(day) {      return day.day == dayname;    });    if (day) {      _.extend(day, properties);    }  }  var days = [{day:'monday'},{day:'tuesday'}];  extendday('monday', {name: 'james'});  extendday('tuesday', {name: 'sandy'});  console.log("after first 2 updates:");  console.log(days);  extendday('monday', {name: 'peter'});  extendday('tuesday', {name: 'joseph'});  console.log("after second 2 updates:");  console.log(days);

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but why weren't seeing code: when console.log array, many consoles make assumption you've used array in "normal" way , not added non-array-entry properties it. code adds non-array-entry properties array.

var days = [{day:'monday'},{day:'tuesday'}];  _.extend(days,{day:'monday'},{name:'peter'});    console.log(days);  console.log(days.day);  console.log(days.name);

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