Javascript regex extract with variable

Question

I'd like to extract values from below key:value pairs being sent in as a single string:

"var1:value1,var2:value2,var3:value3"

I have to use JavaScript and unfortunately I am unable to use an array and loop through the var1,var2,var3 keys due to the regex unable to handle variables... I am wondering if there is a way to do this in JS?

See below:

function onBefore(current, previous) 
{
if (current.key != '' || current.key != null) 
{
    if (current.key.match(/var1/)) {
    var assign = current.key.match(/(?:var1:)([^,]+)/)[1];
    } else if (current.key.match(/var2/)) {
    var assign = current.key.match(/(?:var2:)([^,]+)/)[1];
    } else if (current.key.match(/var3/)) {
    var assign = current.key.match(/(?:var3:)([^,]+)/)[1];
    } else if (current.key.match(/var4/)) {
    var assign = current.key.match(/(?:var4:)([^,]+)/)[1];
    }
    } else {
        assign = "None";
    }
    if (assign != "None") {
    current.node = assign;
    }
}
}

@revo thanks for that answer, for others to benefit... here's the final code:

	var str = "keyIcareabout:test3end,something:value,nothing:burger";
	var node = "None";
	
	function valueOf(key) {
    return (m = (new RegExp("\\b" + key + ":([^,]+)")).exec(str)) !== null ? m[1] : null;
	}
	
	if (str != '' || str !== null) 
	{
		var resources = ["keyIcareabout","somethingelseIcareabout"];
		
		for (i = 0; i < resources.length; i++) 
		{
			if (str.match(resources[i])) 
			{
				node = valueOf(resources[i]);
			}
		}
		
	}
	
	if (node != "None") 
	{
		console.log("Matched " + node + " with node field ");
	}

due to the regex unable to handle variables — what does that mean? — Pointy
– Pointy, Commented Mar 12, 2018 at 22:42
Ok, so may the sample string I provided didn't do judgement to what I am actually dealing with.... xrandom1:xkey1,xrandom2:ykey2,var1:value1,xrandom3:xkey3 yrandom1:ykey1,yrandom2:ykey2,var2:value2,rxandom3:ykey3 And I am only interested in value1 if var1 exists... it may not exist at all... the comment about regex unable to handle variables, i.e. due to the 'extraction', I had to use the ?:xyz: argument which doesn't support variables... or at least doesn't work if I use an array variable to substitute — Dragon Yoon
– Dragon Yoon, Commented Mar 12, 2018 at 22:47

SimpleJ · Accepted Answer · 2018-03-12 22:43:50Z

1

Use String.split:

const data = 'var1:value1,var2:value2,var3:value3';
const pairStrings = data.split(/,/g);
const pairs = pairStrings.map(pairString => pairString.split(/:/));
const object = pairs.reduce((object, [key, value]) => {
  object[key] = value;
  return object;
}, {});

console.log(object);

answered Mar 12, 2018 at 22:43

SimpleJ

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Comments

revo · Accepted Answer · 2018-03-12 23:16:23Z

1

You underestimated RegEx. Your whole function could be shorten to this:

function valueOf(key) {
   return (m = (new RegExp("\\b" + key + ":([^,]+)")).exec(str)) !== null ? m[1] : null;
}

You don't have to check for each key individually in an if condition. Pass key to above valueOf() function to retrieve the value.

var str = "aws_acnt_name:test,aws_acnt_num:1234," +
   "host:identity01.auth-test,region:us-west-2,snow_sg:aws_cloud";

function valueOf(key) {
   return (m = (new RegExp("\\b" + key + ":([^,]+)")).exec(str)) !== null ? m[1] : null;
}

console.log(valueOf('host'));
console.log(valueOf('aws_acnt_name'));

edited Mar 12, 2018 at 23:16

answered Mar 12, 2018 at 22:49

revo

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7 Comments

Dragon Yoon Over a year ago

Sry, the actual var1,var2,var3 is completely different... I just mentioned those as an example... in reality, this would be completely different strings...

Dragon Yoon Over a year ago

there is none, it's actual AWS resource tags... it could be loadbalancername or autoscale_group, etc. i.e. no pattern...

revo Over a year ago

So you have multiple key:value pairs in one single input string that you want to capture each key and corresponding value? @DragonYoon

Dragon Yoon Over a year ago

Yeah, so here is a real example: aws_acnt_name:test,aws_acnt_num:1234,host:identity01.auth-test,region:us-west-2,snow_sg:aws_cloud In there I only want to capture "identity01.auth-test" if the tag "host" exists in the string.

revo Over a year ago

You are doing it right as I see in your question str.match(/host:([^,]+)/)[1]. What's your main problem? @DragonYoon

|

Ori Drori · Accepted Answer · 2018-03-12 22:45:38Z

0

You can use a regex RegExp.exec() to loop through matches of key/value pairs, and extract the key and value to an object (or an array):

var str = 'var1:value1,var2:value2,var3:value3';

var pattern = /([^:,]+):([^,]+)/g;
var obj = {};
var temp;

while(temp = pattern.exec(str)) {
  obj[temp[1]] = temp[2];
}

console.log(obj);

answered Mar 12, 2018 at 22:45

Ori Drori

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Comments

dilip · Accepted Answer · 2018-03-12 23:19:07Z

0

Edit- deleting my answer as suggested by vasan, we need to have quotes around the key and values. Rather than adding quotes and then parsing it will be better to just split it using split function. So SimpleJ's answer should work.

edited Mar 12, 2018 at 23:19

answered Mar 12, 2018 at 22:55

dilip

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1 Comment

Vasan Over a year ago

Did you run this? It would't work. You also need to put quotes around all the keys and values. Very hacky.

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