Fetch elements from JSON using an array in javascript

Question

I have a javascript object which looks like

dict1 =    {"key1":"value1",
             "key2":"value2",
             "key3":"value3",
             "key4":"value4",
             "key5":"value5"}

Next I have got an array which is arr1 = ["key1","key2"]

All I need to do is fetch the value from dict1 based elements in the array and concat them as string.
Sounds fairly Simple:

dict1[arr1[0]] + '-' + dict1[arr1[1]]

Output :

value1-value2

The tricky part for me is that the array arr1 can be of any length but is always the subset of keys present in dict1. For ex:

arr1= ["key2","key5"]
arr1= ["key1","key5","key3"]
arr1= ["key4"]

Based on these input following output is expected:

value2-value5
value1-value5-value3
value4

I am having trouble writing a generic script to create the string dynamically

arr1.map(key=>dict1[key]).join("-")?

acbay
– acbay

2020-05-07 15:21:07 +00:00
Commented May 7, 2020 at 15:21 — acbay
– acbay, Commented May 7, 2020 at 15:21

skovy · Accepted Answer · 2020-05-07 15:23:07Z

3

You can map over the keys you'd like to "pluck" the values from the object and concatenate all of those values together with join.

const dict1 = {
  "key1": "value1",
  "key2": "value2",
  "key3": "value3",
  "key4": "value4",
  "key5": "value5"
}

arr1 = ["key2", "key5"];
arr2 = ["key1", "key5", "key3"];
arr3 = ["key4"];

const pluckAndConcat = (obj, keys) => keys.map(key => obj[key]).join("-");

console.log(pluckAndConcat(dict1, arr1));
console.log(pluckAndConcat(dict1, arr2));
console.log(pluckAndConcat(dict1, arr3));

answered May 7, 2020 at 15:23

skovy

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Comments

Ele · Accepted Answer · 2020-05-07 15:22:15Z

1

You can use the function reduce as follow:

let dict1 =    {"key1":"value1","key2":"value2",             "key3":"value3",             "key4":"value4",             "key5":"value5"};          
let buildString = function(arr, obj) {
  return arr.reduce((a, s) => a.concat(obj[s]), []).join("-")
};

console.log(buildString(["key2","key5"], dict1));
console.log(buildString(["key1","key5","key3"], dict1));
console.log(buildString(["key4"], dict1));

answered May 7, 2020 at 15:22

Ele

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Comments

praveen-me · Accepted Answer · 2020-05-07 15:30:28Z

1

It's simple.

All you need to take a key at a time and get value from your dict and then add that your main string.

Suppose:

let dict1 = {
  "key1":"value1",
  "key2":"value2",
  "key3":"value3",
  "key4":"value4",
  "key5":"value5"
}

You can either use reduce or map.

reduce way:

let genString = (subArray, obj) => subArray.reduce((acc, v, i) => [...acc, obj[v]]  ,[]).join('-')

map way:

let genString = (subArray, obj) => subArray.map((v, i) => obj[v]).join('-')

You can use like this:

genString(["key1","key5","key3"], dict1)

answered May 7, 2020 at 15:30

praveen-me

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