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PatternMatching.js

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/*

Pattern matching is case insensitive as

the inputs are converted to lower case before the

algorithm is run.

The algorithm will run through the entire text and

return the starting index if the given pattern is

available in the text

*/

const checkIfPatternExists = (text, pattern) => {

if (typeof text !== 'string' || typeof pattern !== 'string') {

throw new TypeError('Given input is not a string')

}

const textLength = text.length // Store the length of the text in a variable

const patternLength = pattern.length // Store the length of the pattern in a variable

// Iterate through the text until the textlength - patternlength index

for (let i = 0; i <= textLength - patternLength; i++) {

// For each character in the text check if the subsequent character

// are matching the given pattern; if not break from the condition

for (let j = 0; j < textLength; j++) {

if (text[i + j] !== pattern[j]) break

// For each iteration of j check if the value of

// j + 1 is equal to the length of the pattern

if (j + 1 === patternLength) {

return `Given pattern is found at index ${i}`

}

}

}

}

export { checkIfPatternExists }