Regex filtering in mongoose with partial words?

I am trying to filter result based on a string.
For example- i have to find 'Sanam Suhag'.

When i type 's su' <= this will find the proper result.

But if first word have more then 1 alphabet then i will have to use full first word otherwise it will return empty array.

    router.get('/filter/:keywords', (req, res) => {

    console.log('Keyword recieved in backend ...', req.params.keywords);

    var regex = new RegExp(req.params.keywords, "i")
    var itemFound = Item.find({ name: regex, "status.active": true }, { 'name': 1 }).sort({ "updated_at": -1 }).sort({ "created_at": -1 }).limit(20);
    itemFound.exec((err, data) => {
        console.log(data);
        var result = [];
        if (!err) {
            if (data && data.length && data.length > 0) {
                data.forEach(item => {
                    let itemObj = item
                    result.push(itemObj)
                });
            }
            res.send(result)
        }
        if (err) {
         console.log(err);  
        }
    })
});

Need to find - Sanam Suhag

for 's su' query result - [{name - Sanam Suhag}]

For 'san suhag' query result - []

You should implement the logic to provide the Regex pattern according to the search input.

To summarize the implementation:

1. Split the search input (req.params.keywords) by space.

2. If the first word (firstWord) has more than 1 character, you should use this pattern:

^(?:${firstWord})\s(?:${wordsAfterFirstWord})

Demo Regex pattern 1 @ Regex 101

3. Otherwise, you should use this pattern:

^(?:${firstWord}[\w]+)\s(?:${wordsAfterFirstWord})

Demo Regex pattern 2 @ Regex 101

<!-- begin snippet: js hide: false console: true babel: false -->

<!-- language: lang-js -->

let value = "Sanam Sunag";

// Text search input: "s su"
console.log("Search pattern: 's su', Result: ", getRegexForName("s su").exec(value));


// Text search input: "sam su"
console.log("Search pattern: 'sam su', Result: ", getRegexForName("sam su").exec(value));

function getRegexForName(textSearch) {
    let regexPattern = null;
    
    if (!textSearch)
        return new RegExp("", "i");

    let words = textSearch.split(" ");
    let firstWord = words[0];
    let wordsAfterFirstWord = words.slice(1).join(' ');
    if (words.length == 1)
        return new RegExp(firstWord, "i"); // Or your desired regex pattern that match if the textSearch has single word only

    if (firstWord.length > 1)
        regexPattern = `^(?:${firstWord})\\s(?:${wordsAfterFirstWord})`;
    else
        regexPattern = `^(?:${firstWord}[\\w]+)\\s(?:${wordsAfterFirstWord})`;

    return new RegExp(regexPattern, "i");
}

<!-- end snippet -->

For the caller:

var regex = getRegexForName(req.params.keywords);