2

I have an array of objects in javascript that i want to reduce. See code below. message with 6 or more digits is verified, fewer is unverified. I group them by group.

const myArray = [
 { group: 'groupA', message: 'Text without a number', sl: '1A' },
 { group: 'groupA', message: 'Text with a number WO5467829', sl: '1A' },
 { group: 'groupB', message: 'Text without a number', sl: '1A' },
 { group: 'groupA', message: 'Text with a number WO5467829', sl: '1A' },
 { group: 'groupB', message: 'Text with a number WO5467829', sl: '1A' },
 { group: 'groupC', message: 'Text without a number', sl: '1B' },
 { group: 'groupD', message: 'Text with a number Tick0127866', sl: '1B' },
 { group: 'groupC', message: 'Text without a number', sl: '1A' }
];
output = myArray.reduce((acc, line) => {
 let yes = 0;
 let no = 0;
 line.message.match(/\d{6,}/) ? yes++ : no++;
 acc[line.group] = acc[line.group] || {};
 acc[line.group].verified = (acc[line.group].verified || 0) + yes;
 acc[line.group].unverified = (acc[line.group].unverified || 0) + no;
 return acc;
}, {});
console.log('output', output);

However I would like the output to also be an array of objects like so:

[
 { group: 'groupA', verified: 2, unverified: 1 },
 { group: 'groupB', verified: 1, unverified: 1 },
 { group: 'groupC', verified: 0, unverified: 2 },
 { group: 'groupD', verified: 1, unverified: 0 }
]

How would I do this?

asked Jan 27, 2020 at 16:46
3
  • 2
    Change the logic and use an array (myArray.reduce((acc, line) => ..., [])), or convert the result afterwards with Object.entries() + .map() Commented Jan 27, 2020 at 16:50
  • Can you provide some context regarding why you are trying to achieve? What do you use/need the verified and unverified properties for? Commented Jan 27, 2020 at 16:59
  • Thanks for the swift answers guys! I'll be using the output as input to a d3.js stacked bar chart with monthly figures. Commented Jan 27, 2020 at 17:16

6 Answers 6

3

Use an array as the initial value of your accumulator and inside .reduce , use findIndex to check for the current group, if found, update verified and unverified values, otherwise, insert a new one :

const myArray = [
 { group: "groupA", message: "Text without a number", sl: "1A" },
 { group: "groupA", message: "Text with a number WO5467829", sl: "1A" },
 { group: "groupB", message: "Text without a number", sl: "1A" },
 { group: "groupA", message: "Text with a number WO5467829", sl: "1A" },
 { group: "groupB", message: "Text with a number WO5467829", sl: "1A" },
 { group: "groupC", message: "Text without a number", sl: "1B" },
 { group: "groupD", message: "Text with a number Tick0127866", sl: "1B" },
 { group: "groupC", message: "Text without a number", sl: "1A" }
];
output = myArray.reduce((acc, line) => {
 let yes = 0;
 let no = 0;
 line.message.match(/\d{6,}/) ? yes++ : no++;
 // check if you have the group in the accumulator
 const ndx = acc.findIndex(e => e.group === line.group);
 // if you have it, manipulate verified and unverified
 if (ndx > -1) {
 acc[ndx].verified = (acc[ndx].verified || 0) + yes;
 acc[ndx].unverified = (acc[ndx].unverified || 0) + no;
 } else {
 // insert a new entry instead
 acc.push({
 group: line.group,
 verified: yes,
 unverified: no
 });
 }
 return acc;
}, []); // use an array as the initial value of the accumulator
console.log(output);

answered Jan 27, 2020 at 16:54
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Comments

2

You can simply extend your solution/output to get the actual required output using Object.entries() or Object.keys(). I am going to use Object.entries()

const myArray = [
 { group: 'groupA', message: 'Text without a number', sl: '1A' },
 { group: 'groupA', message: 'Text with a number WO5467829', sl: '1A' },
 { group: 'groupB', message: 'Text without a number', sl: '1A' },
 { group: 'groupA', message: 'Text with a number WO5467829', sl: '1A' },
 { group: 'groupB', message: 'Text with a number WO5467829', sl: '1A' },
 { group: 'groupC', message: 'Text without a number', sl: '1B' },
 { group: 'groupD', message: 'Text with a number Tick0127866', sl: '1B' },
 { group: 'groupC', message: 'Text without a number', sl: '1A' }
];
output = myArray.reduce((acc, line) => {
 let yes = 0;
 let no = 0;
 line.message.match(/\d{6,}/) ? yes++ : no++;
 acc[line.group] = acc[line.group] || {};
 acc[line.group].verified = (acc[line.group].verified || 0) + yes;
 acc[line.group].unverified = (acc[line.group].unverified || 0) + no;
 return acc;
}, {});
console.log('output', output);
const actualOutput = Object.entries(output).map(([group, value]) => ({group, ...value }));
console.log(actualOutput);

answered Jan 27, 2020 at 16:52

Comments

2

I couldn't resist refactoring your code a little. That said. what I have done:

  • initiate the accumulator with an array ( [] )
  • push a group to the array if it is not yet initialised
  • increment verified or unverified depending whether your test fails

const myArray = [
 { group: "groupA", message: "Text without a number", sl: "1A" },
 { group: "groupA", message: "Text with a number WO5467829", sl: "1A" },
 { group: "groupB", message: "Text without a number", sl: "1A" },
 { group: "groupA", message: "Text with a number WO5467829", sl: "1A" },
 { group: "groupB", message: "Text with a number WO5467829", sl: "1A" },
 { group: "groupC", message: "Text without a number", sl: "1B" },
 { group: "groupD", message: "Text with a number Tick0127866", sl: "1B" },
 { group: "groupC", message: "Text without a number", sl: "1A" }
];
output = myArray.reduce((acc, line) => {
 if( acc.findIndex(e => e.group === line.group) === -1 ) {
 	acc.push({
 group: line.group,
 verified: 0,
 unverified: 0
 });
 }
 
 let group = acc.find(e => e.group === line.group);
 if( line.message.match(/\d{6,}/) )
 	group.verified++;
 else
 	group.unverified++;
 return acc;
}, []);
console.log(output);

answered Jan 27, 2020 at 21:37

Comments

1

Put the groupprop in your acc. Then use Object.values function to return the values of an object.

const myArray = [
 { group: 'groupA', message: 'Text without a number', sl: '1A' },
 { group: 'groupA', message: 'Text with a number WO5467829', sl: '1A' },
 { group: 'groupB', message: 'Text without a number', sl: '1A' },
 { group: 'groupA', message: 'Text with a number WO5467829', sl: '1A' },
 { group: 'groupB', message: 'Text with a number WO5467829', sl: '1A' },
 { group: 'groupC', message: 'Text without a number', sl: '1B' },
 { group: 'groupD', message: 'Text with a number Tick0127866', sl: '1B' },
 { group: 'groupC', message: 'Text without a number', sl: '1A' }
];
output = myArray.reduce((acc, line) => {
 let yes = 0;
 let no = 0;
 line.message.match(/\d{6,}/) ? yes++ : no++;
 acc[line.group] = acc[line.group] || {};
 acc[line.group].group = line.group;
 acc[line.group].verified = (acc[line.group].verified || 0) + yes;
 acc[line.group].unverified = (acc[line.group].unverified || 0) + no;
 return acc;
}, {});
console.log('output', Object.values(output));

answered Jan 27, 2020 at 16:50

5 Comments

Someone seems to be downvoting all the answers.
Might just be punishment for answering questions that don't show attempt. But I think the OP's code is close enough, it's not a "write my code for me" question.
@Barmar This attempt is enough. I mean its too much in comparison with the question I usually see of this type.
@MaheerAli Exactly. The reduce code is the hard part.
thanks, was not me downvoting, happy with the assistance
1

You can use map() on Object.entries. I also refactored your code in reduce method 

const myArray = [
 { group: 'groupA', message: 'Text without a number', sl: '1A' },
 { group: 'groupA', message: 'Text with a number WO5467829', sl: '1A' },
 { group: 'groupB', message: 'Text without a number', sl: '1A' },
 { group: 'groupA', message: 'Text with a number WO5467829', sl: '1A' },
 { group: 'groupB', message: 'Text with a number WO5467829', sl: '1A' },
 { group: 'groupC', message: 'Text without a number', sl: '1B' },
 { group: 'groupD', message: 'Text with a number Tick0127866', sl: '1B' },
 { group: 'groupC', message: 'Text without a number', sl: '1A' }
];
let output = myArray.reduce((acc, line) => {
 acc[line.group] = acc[line.group] || {verified: 0, unverified: 0};
 if(line.message.match(/\d{6,}/)){
 acc[line.group].verified++
 }
 else{
 acc[line.group].unverified++
 }
 return acc;
}, {});
output = Object.entries(output).map(([k, v]) => ({group: k, ...v}))
console.log('output', output);

answered Jan 27, 2020 at 16:50

1 Comment

Someone seems to be downvoting all the answers here.
1

Use reduce in combination with regex testing like this - 

const myArray = [{
 group: 'groupA',
 message: 'Text without a number',
 sl: '1A'
 },
 {
 group: 'groupA',
 message: 'Text with a number WO5467829',
 sl: '1A'
 },
 {
 group: 'groupB',
 message: 'Text without a number',
 sl: '1A'
 },
 {
 group: 'groupA',
 message: 'Text with a number WO5467829',
 sl: '1A'
 },
 {
 group: 'groupB',
 message: 'Text with a number WO5467829',
 sl: '1A'
 },
 {
 group: 'groupC',
 message: 'Text without a number',
 sl: '1B'
 },
 {
 group: 'groupD',
 message: 'Text with a number Tick0127866',
 sl: '1B'
 },
 {
 group: 'groupC',
 message: 'Text without a number',
 sl: '1A'
 }
];
const numberRegex = /[0-9]{6}/;
const res = Object.values(myArray.reduce((acc, curr) => {
 const { group, message } = curr;
 const isPhoneVerified = numberRegex.test(message);
 if (!acc[group] && isPhoneVerified) {
 acc[group] = { group: group, verified: 1, unverified: 0 };
 } else if (!acc[group] && !isPhoneVerified) {
 acc[group] = { group: group, verified: 0, unverified: 1 };
 } else if (acc[group] && isPhoneVerified) {
 acc[group].verified += 1;
 } else if (acc[group] && !isPhoneVerified) {
 acc[group].unverified += 1;
 }
 return acc;
}, {}));
console.log(res);

answered Jan 27, 2020 at 17:06

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