4 - 20 August 2021 Coding Creativo 1

JavaScript while loop

by Cristina | Aug 20, 2021 | JavaScript

In this lesson we will talk about the JavaScript while loop and we will also do some very simple examples to understand how it works.

The while is a pre-conditional construct, that is, the condition check occurs before the execution of the instructions indicated in curly brackets.

The syntax of the while loop is as follows:

while (condition) {
   istructions;
}

Where condition represents a Boolean value, that is, a true or false value. The condition determines the length of the cycle that will then run as long as the condition is true.

So as long as the condition is true, the instructions indicated in braces will be executed.

So be careful to set the condition correctly.

The cycle will be infinite if the condition is always true.

While the cycle will never run if the condition is false from the start.

JavaScript while loop – first exercise

Display the numbers 0 to 9 in ascending order.

First we initialize a counter variable to 0 to start from: c = 0.

Then we set the condition in the while, in this case c <10.

Then inside the curly brackets we insert our instructions: we write the variable c and then we increment it by 1.

You will then have these steps:

c = 0

step 1:

the condition: 0 <10 is true:

print 0

increases c by 1: c = 1

step 2:

the condition: 1 <10 is true:

print 1

increases c by 1: c = 2

it is so on until c = 9

So here is the complete code of the while loop in JavaScript.


var c = 0;
while (c < 10){
   document.write(c + '');
   c++;
}

JavaScript while loop - second exercise

Display even numbers from 0 to 100.

To carry out this simple exercise, just change the previous algorithm by increasing c by 2 instead of 1.

We change the condition to also include 100: c <= 100.

We also remember that 0 is an even number.

Here is the complete code:



var c = 0;
while (c <= 100){
   document.write(c + '');
   c += 2;
}

Prev lesson: length

Next lesson: do while

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length of string JavaScript

by Cristina | Aug 20, 2021 | JavaScript

The length of a string in JavaScript is calculated with the length property, that count the amount of characters in that string.

The syntax is therefore the following: string.length, where string represents the string whose length is to be calculated.

length of string JavaScript – example

In this first example we will get the number of characters of any string taken as input.

So here is a possible example to calculate the length of a string:



var sentence = 'do coding creativo';
var sentenceString = sentence.length;
console.log(sentenceString );

In this case, in the browser console we will display the numerical value 20, which corresponds to the number of characters in the sentence.

length of string JavaScript – second example

Determine the length of a string, if it is empty, fill it with the creative coding value, otherwise print the result on the screen.

Suppose we start from an empty string:



var sentence = ' ';

Next, using JavaScript’s length property on strings, we calculate the length of the string and store this data in a variable:



var lengthSentence = sentence.length;

Since the string is empty, the value 0 will be stored in the variable lengthString.

Then, using the conditional statements, we check if the string is not empty and therefore if the length is different from 0 or not. If it is true we display the length of the string, otherwise we set the starting string equal to the example sentence: ‘creative coding’.

Here is a possible implementation:



if (lengthSentence != 0) {
   console.log(lengthSentence );
} else {
   sentence = 'coding creativo';
}

Conclusion

In this lesson we studied how calculate the length of string in JavaScript the JavaScript, similarly the following property can also be used on arrays. You can find the simple example tutorial at the following link: length properties on arrays.

Prev lesson: charCodeAt

Next lesson: while

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JavaScript charCodeAt

by Cristina | Aug 20, 2021 | JavaScript

JavaScript charCodeAt method, to be used on strings, takes an index as an optional parameter. This method returns the Unicode character of the corresponding character specified by the index.

So the syntax is as follows: string.charCodeAt(index).

If the index is not specified, it will have a default value of 0.

Recall that Unicode is an encoding that assigns a unique number to each alphanumeric character. This encoding is independent of the language used.

For more information, see the following link: unicode encoding.

JavaScript charCodeAt

In this first example we will get the Unicode of the first character of a string.

So here’s a possible implementation of the JavaScript charCodeAt method:



var sentence = 'do coding creativo';
var character = sentence.charCodeAt(0);
console.log(character);

So, in the browser console, we get the value 102, which is the corresponding Unicode character of the letter f.

Using the JavaScript charCodeAt method in the last character of a string

In this example we get the Unicode encoding of the last character of a string taken as input.

To do this, it is necessary to use the length property on the string which, remember, returns the number of characters of a given string.

Here is the complete example:



var sentence = 'do coding creativo';
var character = sentence.charCodeAt(sentence.length-1);
console.log(character);

In this case, the value 101 is obtained, which corresponds to the Unicode encoding of the letter o.

If we try to obtain the Unicode encoding of an index that does not exist then we will have the value NaN (Not a Number).

Conclusion

In this lesson we have seen some practical examples on using the JavaScript charCodeAt method, in the next lessons we will see many other examples with other methods on strings and arrays.

Prev lesson: charAt

Next lesson: length

Some useful links