Node.js Assert Complete Reference

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Assert module in Node.js provides a bunch of facilities that are useful for the assertion of the function. The assert module provides a set of assertion functions for verifying invariants. If the condition is true it will output nothing else an assertion error is given by the console.

Example:

Javascript

// Requiring the module 
const assert = require('assert').strict; 
  
var a = "GeeksforGeeks"; 
var b = "Geeks4Geek"; 
  
// Function call 
try { 
    assert.strictEqual(a, b); 
} catch(error) { 
    console.log("Error: ", error) 
}

Output:

Error: AssertionError [ERR_ASSERTION]: Expected values to be strictly equal: + actual – expected + ‘GeeksforGeeks’ – ‘Geeks4Geek’ ^ at Object. (C:\Users\Lenovo\Downloads\index.js:4:12) at Module._compile (internal/modules/cjs/loader.js:1138:30) at Object.Module._extensions..js (internal/modules/cjs/loader.js:1158:10) at Module.load (internal/modules/cjs/loader.js:986:32) at Function.Module._load (internal/modules/cjs/loader.js:879:14) at Function.executeUserEntryPoint [as runMain] (internal/modules/run_main.js:71:12) at internal/main/run_main_module.js:17:47 { generatedMessage: true, code: ‘ERR_ASSERTION’, actual: ‘GeeksforGeeks’, expected: ‘Geeks4Geek’, operator: ‘strictEqual’ }

The Complete List of NodeJS Assert are listed below:an

NodeJS Assert	Description
Node.js assert() Function	If the value is not the truth, then a AssertionError is thrown with a message property set equal to the value of the message parameter.
Node.js assert.deepStrictEqual() Function	The assert.deepStrictEqual() function tests for deep equality between the actual and expected parameters.
Node.js assert.doesNotThrow() Function	The assert.doesNotThrow() function asserts that the function fn does not throw an error.
Node.js assert.equal() Function	The assert.equal() function tests for equality between the actual and the expected parameters.
Node.js assert.fail() Function	The assert.fail() function throws an AssertionError with the provided error message or with a default error message.
Node.js assert.ifError() Function	The assert.ifError() function throws a value if the value is not defined or null.
Node.js assert.match() Function	The assert.match() function expects the string input to match the regular expression.
Node.js assert.notDeepEqual() Function	The assert.notDeepEqual() function tests deep strict inequality between the actual and the expected parameters.
Node.js assert.notDeepStrictEqual() Function	The assert.notDeepStrictEqual() function tests for deep strict inequality.
Node.js assert.notEqual() Function	The assert.notEqual() function tests strict inequality between the actual and the expected parameters.
Node.js assert.ok() Function	The assert module provides a set of assertion functions for verifying invariants.
Node.js assert.rejects() Function	The assert.rejects() function awaits the asyncFn promise
Node.js assert.strictEqual() Function	The assert.strictEqual() function tests strict equality between the actual and expected parameters.

Last Updated : 05 Dec, 2022

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