Jquery Run Function Check Variable Then Run Again if True

There will exist times where y'all will desire to write commands that handle unlike decisions in your code.

For case, if you lot are coding a bot, y'all can have it answer with different messages based on a set of commands it receives.

In this article, I will explain what an if...else argument is and provide lawmaking examples. We will also await at the conditional (ternary) operator which yous can use equally a autograph for the if...else statement.

What is an if...else statement in JavaScript?

The if...else is a type of conditional statement that volition execute a block of code when the condition in the if statement is truthy. If the status is falsy, so the else block will be executed.

Truthy and falsy values are converted to true or false inif statements.

                if (condition is true) {    // lawmaking is executed } else {    // code is executed }              

Any value that is non defined equally falsy would be considered truthy in JavaScript.

Here is a list offalsy values:

• false
• 0 (zero)
• -0 (negative zero)
• 0n (BigInt zero)
• "", '', `` (empty string)
• null
• undefined
• NaN (not a number)

Examples of if...else statements in JavaScript

In this instance, the condition for the if statement is true so the message printed to the console would be "Nick is an adult."

                const historic period = xviii;  if (age >= 18) {   console.log("Nick is an adult."); } else {   console.log("Nick is a child."); }              

But if I modify the age variable to be less than 18, then the condition would be imitation and the code would execute the else block instead.

                const age = 12;  if (historic period >= 18) {   console.log("Nick is an developed."); } else {   console.log("Nick is a child."); }              

Examples of multiple weather (if...else if...else statements) in JavaScript

There will exist times where you lot want to test multiple weather condition. That is where the else if block comes in.

                if (status 1 is truthful) {    // lawmaking is executed } else if (condition 2 is truthful) {   // code is executed } else {    // code is executed }              

When the if argument is false, the computer will move onto the else if argument. If that is besides false, and so it will motion onto the else block.

In this case, the else if block would be executed considering Alice is between the ages of 18 and 21.

                const age = eighteen;  if (age < eighteen) {   console.log("Alice is nether 18 years one-time."); } else if (age >= xviii && age <= 21) {   console.log("Alice is between the ages of 18 and 21."); } else {   panel.log("Alice is over 21 years old."); }              

When to use switch statements over if...else statements?

There are times in JavaScript where you might consider using a switch argument instead of an if else statement.

switch statements tin have a cleaner syntax over complicated if else statements.

Take a look at the example below – instead of using this long if else statement, you might choose to go with an easier to read switch statement.

                const pet = "domestic dog";  if (pet === "lizard") {   console.log("I own a cadger"); } else if (pet === "dog") {   console.log("I own a dog"); } else if (pet === "cat") {   panel.log("I own a cat"); } else if (pet === "snake") {   console.log("I own a snake"); } else if (pet === "parrot") {   console.log("I own a parrot"); } else {   panel.log("I don't own a pet"); }              

                const pet = "dog";   switch (pet) {   case "lizard":     console.log("I own a lizard");     suspension;   case "dog":     panel.log("I own a dog");     break;   case "cat":     console.log("I own a cat");     break;   case "serpent":     console.log("I own a ophidian");     break;   case "parrot":     console.log("I own a parrot");     break;   default:     console.log("I don't ain a pet");     break; }              

switch statements will non be advisable to use in all situations. Just if you experience like the if else statements are long and complicated, then a switch statement could be an alternative option.

The logical AND (&&) operator and if...else statements in JavaScript

In the logical AND (&&) operator, if both conditions are true, then the if cake will be executed. If one or both of the conditions are simulated, and so the else block will exist executed.

In this case, since historic period is greater than 16 and the ownsCar variable is truthful, the if cake volition run. The message printed to the console will be "Jerry is old plenty to drive and has his ain car."

                const historic period = 17; const ownsCar = true;  if (age >= 16 && ownsCar) {   console.log("Jerry is old enough to drive and has his own auto."); } else {   panel.log("Jerry does non drive."); }              

If I modify the age variable to exist less than sixteen, then both conditions are no longer true and the else block would be executed instead.

                const age = 13; const ownsCar = true;  if (age >= 16 && ownsCar) {   console.log("Jerry is old enough to drive and has his own motorcar."); } else {   console.log("Jerry does not drive."); }              

The logical OR (||) operator and if...else statements in JavaScript

In the logical OR (||) operator, if 1 or both of the weather condition are truthful, then the code inside the if statement will execute.

In this example, even though the isSale variable is set to faux, the code inside the if block will still execute considering the boyfriendIsPaying variable is fix to true.

                const boyfriendIsPaying = true; const isSale = simulated;  if (boyfriendIsPaying || isSale) {   console.log("Jesse will become shopping."); } else {   console.log("Jesse will non get shopping."); }              

If I were to modify the value of the boyfriendIsPaying variable to false, and so the else cake would execute because both conditions are false.

                const boyfriendIsPaying = false; const isSale = faux;  if (boyfriendIsPaying || isSale) {   console.log("Jesse will go shopping."); } else {   console.log("Jesse will not get shopping."); }              

The logical NOT (!) operator and if...else statements in JavaScript

The logical NOT (!) operator will take something that is true and make it simulated. Information technology will besides take something that is false and make it true.

We can alter the example from earlier to employ the ! operator to make the boyfriendIsPaying variablefalse. Since both weather condition are simulated, the else block would be executed.

                const boyfriendIsPaying = true; const isSale = faux;  if (!boyfriendIsPaying || isSale) {   panel.log("Jesse volition go shopping."); } else {   console.log("Jesse volition not go shopping."); }              

Conditional (ternary) operator in JavaScript

If you lot have a short if else statement, then you might choose to go with the ternary operator.  The discussion ternary ways something composed of iii parts.

This is the bones syntax for a ternary operator:

                condition ? if condition is true : if condition is faux                              

The condition goes before the ? mark and if it is true, then the lawmaking betwixt the ? marking and : would execute. If the condition is false, then the code after the: would execute.

In this example, since age is greater than 18, then the bulletin to the console would be "Can vote".

                const age = 32; const citizen = age >= xviii ? "Can vote" : "Cannot vote"; console.log(citizen);                              

This is what the code would look like using an if else statement:

                const historic period = 32; let citizen;  if (age >= 18) {   citizen = "Can vote"; } else {   denizen = "Cannot vote"; }  console.log(citizen);              

Decision

if else statements will execute a block of code when the condition in the if statement is truthy. If the status is falsy, then the else block will be executed.

There will be times where yous desire to exam multiple conditions and you tin can use an if...else if...else argument.

If you experience like the if else argument is long and complicated, then a switch statement could exist an alternative option.

Using logical operators to test multiple weather can supercede nested if else statements.

The ternary operator can be used to write shorter code for a elementary if else statement.

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Source: https://www.freecodecamp.org/news/javascript-if-else-and-if-then-js-conditional-statements/

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