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JavaScript: Generate a UUID in a browser

JavaScript fundamental (ES6 Syntax): Exercise-253 with Solution

Write a JavaScript program to generate a UUID in a browser.

  • Use Crypto.getRandomValues() to generate a UUID, compliant with RFC4122 version 4.
  • Use Number.prototype.toString(16) to convert it to a proper UUID.

Sample Solution:

JavaScript Code:

//#Source https://bit.ly/2neWfJ2 
const UUIDGeneratorBrowser = () =>
  ([1e7] + -1e3 + -4e3 + -8e3 + -1e11).replace(/[018]/g, c =>
    (c ^ (crypto.getRandomValues(new Uint8Array(1))[0] & (15 >> (c / 4)))).toString(16)
  );
console.log(UUIDGeneratorBrowser());

Sample Output:

a47704c1-b9cb-481d-bada-bd6495a88ef7

Flowchart:

flowchart: Generate a UUID in a browser.

Live Demo:

See the Pen javascript-basic-exercise-253-1 by w3resource (@w3resource) on CodePen.


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Next: Write a JavaScript program to generate a UUID in Node.JS. Use crypto API to generate a UUID, compliant with RFC4122 version 4.

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JavaScript: Tips of the Day

Checking if a key exists in a JavaScript object?

Checking for undefined-ness is not an accurate way of testing whether a key exists. What if the key exists but the value is actually undefined?

var obj = { key: undefined };
obj["key"] !== undefined // false, but the key exists!

You should instead use the in operator:

"key" in obj // true, regardless of the actual value

If you want to check if a key doesn't exist, remember to use parenthesis:

!("key" in obj) // true if "key" doesn't exist in object
!"key" in obj   // ERROR!  Equivalent to "false in obj"

Or, if you want to particularly test for properties of the object instance (and not inherited properties), use hasOwnProperty:

obj.hasOwnProperty("key") // true

Checking for undefined-ness is not an accurate way of testing whether a key exists. What if the key exists but the value is actually undefined? var obj = { key: undefined }; obj["key"] !== undefined // false, but the key exists! You should instead use the in operator: "key" in obj // true, regardless of the actual value If you want to check if a key doesn't exist, remember to use parenthesis: !("key" in obj) // true if "key" doesn't exist in object !"key" in obj // ERROR! Equivalent to "false in obj" Or, if you want to particularly test for properties of the object instance (and not inherited properties), use hasOwnProperty: obj.hasOwnProperty("key") // true For performance comparison between the methods that are in, hasOwnProperty and key is undefined.

Ref: https://bit.ly/2CFNp1X