JavaScript Ojbects: Add and Change Name:Value Pairs

Hongtao Hao / 2021-08-02


Take the following as an example

data = [
  { "date" : '2013-01-01', "value" : 45 },
  { "date" : '2013-02-01', "value" : 50 },
  { "date" : '2013-03-01', "value" : 55 },
  { "date" : '2013-04-01', "value" : 50 },
  { "date" : '2013-05-01', "value" : 45 },
  { "date" : '2013-06-01', "value" : 50 },
  { "date" : '2013-07-01', "value" : 50 },
  { "date" : '2013-08-01', "value" : 52 }
]

How to add new name:value pairs #

data.map(function(d) {
  d.valuePlus = d.value + 1;
  return d;
})

Or:

data.map(d => {
  d.valuePlus = d.value + 1;
  return d;
})

How to change names in the object’s name:value pairs #

This is basically to create a new object or a new array of objects

data.map(function(d) {return {
  "newdate": d.date,
  "newvalue": d.value,
}})

Or

data.map(d => ({
  "newdate": d.date,
  "newvalue": d.value,
}))

Note that in the second arrow function (right above), we use parentheses around object literals to let the function return “a single value”, which is an object.

We don’t need parenthese in the first arrow function because “curly braces are execuating multiple lines of codes”, quoting david .

Last modified on 2021-10-24