If-else statement
Sometimes, one condition is not enough, and for that, in TypeScript (as in other programming languages), there is the if-else
construct. For example, if you need to create a calculator, you, as a true programmer, will do it using the if-else
construct, like this:
1234567891011121314let a: number = 5; let b: number = 10; let operator: string = '*'; if (operator == '+') { console.log(a + b); } else if (operator == '-') { console.log(a - b); } else if (operator == '*') { console.log(a * b); } else if (operator == '/') { console.log(a / b); } else { console.log(`Error, there is no ${operator} operator!`) }
In this code, we have 3 variables: number a
, number b
, and the operation that will be performed between them. Using the if-else
construct, we determine which operation will be applied to these two numbers. If we don't find a suitable operation, we will display a message indicating that such an operation is not available!
Now let's take a closer look at the syntax we're using:
javascript99123456789101112if (first_condition) {// code block if the first condition is true} else if (second_condition) {/* A block of code that will executeif the first condition is falseand the second condition is true. */} else if... {// You can have as many of these blocks as you want.} else {/* A block of code that will executeif all previous conditions are false. */}
Note that if one of the conditions is met, we exit the if-else
statement, and the remaining blocks are ignored.
Unlike else if
, the else
block does not have a condition block. This is because else executes only if all previous conditions were false
.
The if-else
construct is often used for a variety of tasks, from checking if a number is positive to writing artificial intelligence.
You can also choose not to use else-if
blocks and use only if
and else
, for example:
123456let num: number = 15; if (num >= 0) { console.log('The number is positive!'); } else { console.log('The number is negative'); }
This way, we can experiment and use such a construct for various purposes!
1. What is the purpose of the if-else
statement in TypeScript?
2. In an if-else
statement, what is executed if the condition inside the if
block is false?
Thanks for your feedback!
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