JavaScript: Count the occurrence of a substring in a string
JavaScript String: Exercise-18 with Solution
Write a JavaScript function to count the occurrence of a substring in a string.
Test Data:
console.log(count("The quick brown fox jumps over the lazy dog", 'the'));
Output:
2
console.log(count("The quick brown fox jumps over the lazy dog", 'fox',false));
Output:
1
Pictorial Presentation:
Sample Solution-1:
JavaScript Code:
function count(main_str, sub_str)
{
main_str += '';
sub_str += '';
if (sub_str.length <= 0)
{
return main_str.length + 1;
}
subStr = sub_str.replace(/[.*+?^${}()|[\]\\]/g, '\\$&');
return (main_str.match(new RegExp(subStr, 'gi')) || []).length;
}
console.log(count("The quick brown fox jumps over the lazy dog", 'the'));
console.log(count("The quick brown fox jumps over the lazy dog", 'fox',false));
Sample Output:
2 1
Flowchart:
Sample Solution-2:
Counts the occurrences of a substring in a given string.
- Use Array.prototype.indexOf() to look for searchValue in str.
- Increment a counter if the value is found and update the index, i.
- Use a while loop that will return as soon as the value returned from Array.prototype.indexOf() is -1.
JavaScript Code:
//Source:https://bit.ly/3hEZdCl
// countSubstrings
const count_substr = (str, searchValue) => {
let count = 0,
i = 0;
while (true) {
const r = str.indexOf(searchValue, i);
if (r !== -1) [count, i] = [count + 1, r + 1];
else return count;
}
};
console.log(count_substr("The quick brown fox jumps over the lazy dog", 'the'));
console.log(count_substr("The quick brown fox jumps over the lazy dog", 'fox'));
Sample Output:
1 1
Flowchart:
Live Demo:
See the Pen JavaScript Count the occurrence of a substring in a string - string-ex-18 by w3resource (@w3resource) on CodePen.
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Next: Write a JavaScript function to escape a HTML string.
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JavaScript: Tips of the Day
How to insert an item into an array at a specific index (JavaScript)?
What you want is the splice function on the native array object.
arr.splice(index, 0, item); will insert item into arr at the specified index (deleting 0 items first, that is, it's just an insert). In this example we will create an array and add an element to it into index 2:
var arr = []; arr[0] = "Jani"; arr[1] = "Hege"; arr[2] = "Stale"; arr[3] = "Kai Jim"; arr[4] = "Borge"; console.log(arr.join()); arr.splice(2, 0, "Lene"); console.log(arr.join());
Ref: https://bit.ly/2BXbp04
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