getWordPos.js

// Solution 1 without regex

function isLowerAlpha(char) {
    return /^[a-z]+$/.test(char);
}

function getWordPos(word, text) {
    for (var i = 0; i <= text.length - word.length; i++) {
        if (text.substr(i, word.length) === word) {
            if (i === 0 || !isLowerAlpha(text.charAt(i - 1))) {
                if (
                    i + word.length === text.length ||
                    !isLowerAlpha(text.charAt(i + word.length))
                ) {
                    return i;
                }
            }
        }
    }
    return -1;
}

// Solution 2 regex

function getWordPos(word, text) {
    const filterText = text.replace(/[.,\/#!$%\^&\*;:{}=\-_`~()]/g, "");
    const parts = filterText.split(/\s+/);

    for (let i = 0; i < parts.length; i++) {
        if (parts[i] === word) {
            const match = new RegExp(`\\b${word}\\b`, "g").exec(text);
            return match ? match.index : -1;
        }
    }

    return -1;
}

function runPlainTest(arr) {
    arr.forEach((val) => {
        const res = getWordPos(val.word, val.text);
        if (res !== val.result) {
            throw new Error(
                `Test faild for ${JSON.stringify(val, null, 2)}` +
                    `\nexpected ${res} but passed ${val.result}`
            );
        }
    });
    console.log("All test cases passed!!");
}


const testSamples = [
    {
        word: "is",
        text: "this !!is a string",
        result: 7,
    },
    {
        word: "is",
        text: "this (is a string",
        result: 6,
    },
    {
        word: "is",
        text: "this (is) a string",
        result: 6,
    },
    {
        word: "is",
        text: "this  is a string",
        result: 6,
    },
    {
        word: "is",
        text: "this is a string",
        result: 5,
    },
    {
        word: "not",
        text: "this is a string",
        result: -1,
    },
    {
        word: "string",
        text: "this is a string",
        result: 10,
    },
    {
        word: " ",
        text: "this is a string",
        result: -1,
    },
];

runPlainTest(testSamples);