Reduce array in javascript with patern matching

Question

How would you reduce items from array arr into reducedArray by removing items that first two characters match with strings from array generalCase and if they encountered, then an asterisk is added to indicated that this string was encountered on array arr.

let arr =["ADB", "AB1", "BD1", "BD4", "AB3", "BP9", "BPX","STR", "ABS"]
let generalCase = ["AB", "BD", "BP"]
let reducedArray = []

arr.forEach( item => {
  if (item.startsWith("AB") && !reducedArray.includes("AB*")) {
        reducedArray.push("AB*");
      } else if (item.startsWith("BD") && !reducedArray.includes("BD*")) {
        reducedArray.push("BD*")
      } else if (item.startsWith("BP") && !reducedArray.includes("BP*")) {
        reducedArray.push("BP*")
      } else if (item === "STR") {
        reducedArray.push("STR")
      } else if (!reducedArray.includes(item)) {
        reducedArray.push(item)
      }
})

// Desired result: ["ADB", "AB*", "BD*", "BP*", "STR"]
console.log(reducedArray) // ["ADB", "AB*", "BD*", "BD4", "AB3", "BP*", "BPX", "STR", "ABS"]

adiga · Accepted Answer · 2023-01-05 13:18:11Z

1

You could create a regex from the generalCase array to test if any of the strings in arr start with any of them.

In this case, it creates a regex like this:

/^(?:AB|BD|BP)/

Here's a snippet:

const arr = ["ADB", "AB1", "BD1", "BD4", "AB3", "BP9", "BPX", "STR", "ABS"],
      generalCase = ["AB", "BD", "BP"],
      regex = new RegExp(`^(?:${generalCase.join("|")})`),
      set = new Set;

for (const str of arr) {
  if (regex.test(str))
    set.add(str.slice(0, 2) + "*")
  else
    set.add(str)
}

console.log([...set])

answered Jan 5, 2023 at 13:18

adiga

35.4k9 gold badges65 silver badges88 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

0stone0 · Accepted Answer · 2023-01-05 12:51:10Z

0

Use reduce():

const arr = ["ADB", "AB1", "BD1", "BD4", "AB3", "BP9", "BPX","STR", "ABS"];
const generalCase = ["AB", "BD", "BP"];

const reducedArray = arr.reduce((p, c) => {
    const firsttwo = c.substring(0,2);
    const toPush = (generalCase.includes(firsttwo)) ? (firsttwo + '*') : c;
    
    if (!p.includes(toPush)) {
        p.push(toPush);
    }
    
    return p;
}, []);

console.log(reducedArray);

Result:

[
  "ADB",
  "AB*",
  "BD*",
  "BP*",
  "STR"
]

edited Jan 5, 2023 at 12:51

answered Jan 5, 2023 at 12:46

0stone0

45.5k6 gold badges53 silver badges82 bronze badges

Comments

gog · Accepted Answer · 2023-01-05 12:48:23Z

0

Iterate normally, and deduplicate the result in the end:

let arr =["ADB", "AB1", "BD1", "BD4", "AB3", "BP9", "BPX","STR", "ABS"]
let generalCase = ["AB", "BD", "BP"]

let reducedArray = arr.map(item => {
    for (let x of generalCase)
        if (item.startsWith(x))
            return x + '*'
    return item
})


reducedArray = [...new Set(reducedArray)]

console.log(reducedArray)

answered Jan 5, 2023 at 12:48

gog

11.4k2 gold badges29 silver badges42 bronze badges

Collectives™ on Stack Overflow

Reduce array in javascript with patern matching

3 Answers 3

Comments

Result:

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

Comments

Result:

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related