Answer Category: TypeScript

How to check variable is null or undefined?

Post author By Mubarak Hossain
Post date May 5, 2023

To check for null or undefined in TypeScript, use a comparison to check if the value is equal or is not equal to null or undefined.

Check example below:

// check val variable value
if(typeof val=='undefined' || val=="" || val==null){
	// null
} else {
	// not null
}

How to filter numeric value and remove if 1st character is zero?

Post author By Mubarak Hossain
Post date May 5, 2023

In below example will see how to filter numeric value (1-9) and remove all unnecessary characters and if 1st character is zero from a string by using regular expression and charAt method.

// My string variable
const myString = '0171D82d584';

// We filtered and exclude characters and 1st 0 form a string
const filteredString = myString.replace(/[^0-9]/g, '');
while(filteredString.charAt(0)===0)
{
	filteredString = filteredString.substring(1);
}
console.log('Result:', filteredString);

// Output results
// Result: 17182584

How to filter numeric value and remove all unnecessary characters?

Post author By Mubarak Hossain
Post date May 5, 2023

In below example will see how to filter numeric value (0-9) and remove all unnecessary characters from a string by using regular expression.

// My string variable
const myString = '0171D82d584';

// We filtered and exclude characters form a string
const filteredString = myString.replace(/[^0-9]/g, '');
console.log('Numeric Value:', filteredString);

// Output results
// Numeric Value: 017182584

How to loop an array of objects and print some key value?

Post author By Mubarak Hossain
Post date May 5, 2023

I used the map() method to iterate over the array of object. In objectItems has some array of object items. In below example will see how to map an array of objects and iterate over the array of object and write console log product ID and product Name by using TypeScript or Javascript.

// My data object
const objectItems = [
	{productId: 1, productName: 'Porduct 01'},
	{productId: 2, productName: 'Porduct 02'},
	{productId: 3, productName: 'Porduct 03'}
];

// We filtered and exclude third item form object
objectItems.map((item, index)=>{
	console.log('ProductId:', item.productId);
	console.log('ProductName:', item.productName);
});

// Output results
/*
ProductId: 1
ProductName: Porduct 01

ProductId: 2
ProductName: Porduct 02

ProductId: 3
ProductName: Porduct 03
*/

How to filter an array of objects in TypeScript?

Post author By Mubarak Hossain
Post date May 5, 2023

I used the filter() method to iterate over the array of object. In objectItems has some array of object items. I have iterate over the array and checked & compaire eventId & productId, if eventId not equal 3 & productId not equal 8 in object objectItems meets those conditions.

// My data object
const objectItems = [
	{eventId: 1, productId: 6, productName: 'Porduct 01'},
	{eventId: 2, productId: 7, productName: 'Porduct 02'},
	{eventId: 3, productId: 8, productName: 'Porduct 03'},
	{eventId: 4, productId: 9, productName: 'Porduct 04'},
	{eventId: 5, productId: 10, productName: 'Porduct 05'},
	{eventId: 6, productId: 11, productName: 'Porduct 06'}
];

// We filtered and exclude third item form object
const filteredObjectItems = objectItems.filter(function( obj ) {
	return (obj.eventId !== 3 && obj.productId !== 8);
});

// Filtered object return Output
[
	{eventId: 1, productId: 6, productName: 'Porduct 01'},
	{eventId: 2, productId: 7, productName: 'Porduct 02'},
	{eventId: 4, productId: 9, productName: 'Porduct 04'},
	{eventId: 5, productId: 10, productName: 'Porduct 05'},
	{eventId: 6, productId: 11, productName: 'Porduct 06'}
];

Related Answers

Related Answers

Related Answers

Related Answers

Related Answers

Recent Posts

Categories

Important Links