Extract key value from string with regex in JavaScript

Question

I need a function to extract key values from an string like this: 

I want to make an standard function to extract any value. The call is something like this: var name=ExtractValue(text,"Name");

This is my approach:

var text="<!-- Name:Peter Smith --><!-- Age:23 -->"; // Data to be scanned

var name=ExtractValue(text,"Name"); // Get the "Name" key value
var age=ExtractValue(text,"Age");   // Get the "Age" key value
document.getElementById("result").innerHTML = "Extracted name: ("+name+"), age: ("+age+")";

// Function for extranting key values
function ExtractValue(data,key){
    // It's try to be like /Name:(.*)\s--/
    var rx = "/"+key+"(.*)\s--/";
    var values = rx.exec(data);
    if(values.lenght>0){
        return values[1];
    } else{
        return "";
    }
}

How can I do this? Thanks for your time!

Here's an example how to create a Regex that support similar data format: regex101.com/r/euwxBp/1 Since you're in JavaScript land, I'd convert the data to to an object, for its native key-value support, and then lookup 'keys' by getting the obj[key] ref and checking if it exists. P.S. - You haven't mentioned what key and data formats should be supported - so the Regex is pretty basic. — Elia Grady
– Elia Grady, Commented Feb 26, 2017 at 9:13

trincot · Accepted Answer · 2017-02-26 18:45:42Z

3

You can do it like this:

var text="<!-- Name:Peter Smith --><!-- Age:23 -->"; // Data to be scanned

var name=ExtractValue(text,"Name"); // Get the "Name" key value
var age=ExtractValue(text,"Age");   // Get the "Age" key value
console.log("Extracted name: ("+name+"), age: ("+age+")");

function ExtractValue(data,key){
    var rx = new RegExp(key + ":(.*?)\\s+--");
    var values = rx.exec(data); // or: data.match(rx);
    return values && values[1];
}

Don't forget to escape backslashes in a string literal. So "\\s" instead of "\s", as the latter would be exactly the same as "s". Also, the colon was missing in your regular expression. Finally, you had a spelling mistake in the length property name, so your if condition would always be false.

Be aware that exec and match will return null when there is no match, so you should not assume there is a length property.

edited Feb 26, 2017 at 18:45

answered Feb 26, 2017 at 9:18

trincot

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Comments

dodov · Accepted Answer · 2017-02-26 09:46:32Z

0

This approach returns an object with all the found key/value pairs. From there, you can search for any key you want.

var text = "<!-- Name:Peter Smith --><!-- Age:23 --><!-- Key with  space  : yes -->";

var data = ExtractData(text);
console.log(data);
console.log("Extracted name: (" + data["Name"] + "), age: (" + data["Age"] + ")");

function ExtractData(data) {
  var matches = data.match(/([A-Za-z\s]+:[^\-\-\>]+)/g);
  var data = {};

  if (Array.isArray(matches)) {
    matches.forEach(function(match) {
      var pair = match.split(":");
      if (pair.length === 2) {
        data[pair[0].trim()] = pair[1].trim();
      }
    });
  }

  return data;
}

edited Feb 26, 2017 at 9:46

answered Feb 26, 2017 at 9:41

dodov

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Comments

burkay · Accepted Answer · 2017-02-26 10:53:44Z

0

Instead of regex, you can use string split function.

var text = "<!-- Name:Peter Smith --><!-- Age:23 -->"; // Data to be scanned
var obj = ExtractToObj(text);
document.getElementById("result").innerHTML = "Extracted name: (" + obj["Name"] + "), age: (" + obj["Age"] + ")";

function ExtractToObj(data) {
  var obj = {};
  var kvps = data.split("-->").filter(function(n) {
    return n !== ""; // remove empty elements
  });
  for (var i = 0; i < kvps.length; i++) {
    var kvp = kvps[i].split(":");
    var key = kvp[0].replace("<!--", "").trim();
    var value = kvp[1].trim();
    obj[key] = value;
  }
  return obj;
}

https://jsfiddle.net/ydjbc4yq/

answered Feb 26, 2017 at 10:53

burkay

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Comments

Maciej Kozieja · Accepted Answer · 2017-02-26 14:58:57Z

0

I would do something like this:

const data = `<div><!-- Name   : Peter Smith --><!-- Age:23 -->some test data that is not found</div>`

const getData = data => {
  const obj = {}, regex = /<!--\s*(.*?)\s*:\s*(.*?)\s*-->/g
  let temp
  while (temp = regex.exec(data)){
    obj[temp[1]] = temp[2]
  }
  return obj
}

const personInfo = getData(data)
console.log(`Extracted name: (${personInfo.Name}), age: (${personInfo.Age})`)

Or if you want to extract only one property:

const data = `<div><!-- Name   : Peter Smith --><!-- Age:23 -->some test data that is not found</div>`

const getData = (data, key) => (data.match(new RegExp(`<!--\\s*${key}\\s*:\\s*(.*?)\\s*-->`)) || [, null])[1]

console.log(`${getData(data, 'Name')}`)

edited Feb 26, 2017 at 14:58

answered Feb 26, 2017 at 14:47

Maciej Kozieja

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