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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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