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Mansoor Ahmed Selected

Mansoor Ahmed

1 year ago
We use Strings for holding data. That data may be represented in text form. Several of the maximum-used operations on strings are;

To check their length,
To form and concatenate them using the + and += string operators,
Testing for the existence or location of substrings with the indexOf() method,
Removing substrings with the substring() method.

How to Create a String?
We can create a String by way of primitives, from string literals, or as objects, using the String() constructor:

const string1 = “A string primitive”;

const string2 = ‘Also a string primitive’;

const string3 = `Yet another string primitive`;

const string4 = new String(“A String object”);

Enduringly bear in mind

A string is indexed similarly to an array.
Simply, in place of each index number referring to an element, it states to a character.
Identical array indexing, string indexing initiates with 0.
The first number inside the parentheses is the index of the first character in the slice as per the slice method.
The second number is not, though, the last character in the slice.
It’s the first character after the slice.
If we subtract the first index from the second index, we’ll at all times get the length of the slice.

How to find & replace the banned segment
What if, the paragraph below has been assigned to the variable text.

1 for (var i = 0; i

if (text.slice(i, i + 12) === “World War II”) {
text = text.slice(0, i) + “the Second World War” + text.slice(i + 12);
The code loops over the string looking for World War II. Line 2 grows through the string character-by-character, inspecting each 12-character sequence. Line 3 concatenates three segments if it discovers World War II: totally the characters prior to World War II, the standby phrases “the Second World War,” and then all the characters following World War II…

By using the indexOf method in JavaScript

var firstChar = text.indexOf(“World War II”);

The method discovers the index of the first character of the segment and assigns it to the variable firstChar if the segment exists. The method assigns -1 to the variable; consequently, we know it’s not there if the segment doesn’t exist.

Now we may change the banned phrase with the preferred phrase with less coding.

var firstChar = text.indexOf(“World War II”);
if (firstChar!== -1) {
text = text.slice(0, firstChar) + “the Second World War” + text.slice(firstChar + 12);
Line 1 checks for the phrase, if the phrase is found, assigning the index of the first character of the phrase to the variable firstChar and, -1 is assigned to the variable if it isn’t set up.

Line 2 if the variable doesn’t have the value -1 and if the phrase has been found—the concatenation in line 3 switches the wrong phrase by the correct phrase. The indexOf method finds only the first example of the segment we’re looking for. In the illustration above, we could overcome this curb by looping. We’d change the first example of “World War II” to “the Second World War,” then in the next loop iteration, find the next persisting illustration and change that, and so on. Use lastIndexOf to find the last example of a segment in a string. The below code finds the index of the first character of the last case in point of the segment, the second “be”. The variable segIndex winds up through a value of 16, the index of “b” in the second “be”.

var text = “To be or not to be.”;
var segIndex = text.lastIndexOf(“be”);
How to access the Character
We use two methods to access an individual character in a string. The first method is the charAt() method:

return ‘cat’.charAt(1) // returns “a”

The second method has been introduced in ECMAScript 5. That is a way to treat the string as an array-like object, wherever distinct characters resemble a numerical index:

return ‘cat'[1] // returns “a”

The properties involved are neither writable nor configurable. Once using bracket notation for character access, trying to delete or allocate a value to these properties would not do well.

How to replace the Characters
JavaScript makes available an additional direct way still, the replace method to replace the characters.

var newText = text.replace(“World War II”, “the Second World War”);

The first string inside the parentheses is the segment to be changed. The second string is the segment to be introduced. The segment “World War II” is changed by the segment “the Second World War” in the string represented by the variable text. The go-through string is assigned to the new variable newText in the above code. The unique string is preserved if we assign the revised string to a new variable, for example in the instance above. Assign the reread string to the original variable if we want the original string to be changed with the revised string.

text = text.replace(“World War II”, “the Second World War”);

In the illustrations above, simply the first instance of a string is changed. We must let JavaScript know that we want a global replacement in case if we want to change all instances.

var newText = text.replace(/World War II/g, “the Second World War”);

We surround the segment to be changed with slashes instead of quotation marks in a worldwide replacement. Follow the closing slash with “g” for “global.” The segment to be introduced is surrounded by quotation marks, as in a one-time replacement.