1 line of code: How to truncate a string at word boundaries

const truncateAfterWord = (str, chars, placeholder = '…') =>  str.length < chars ? str : `${str.substr( 0, str.substr(0, chars - placeholder.length).lastIndexOf(" "))}${placeholder}`;

Returns the string truncated to the given amount of chars while preserving full words.

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The repository & npm package

You can find the all the utility functions from this series at github.com/martinkr/onelinecode
The library is also published to npm as @onelinecode for your convenience.

The code and the npm package will be updated every time I publish a new article.

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Comments

[John Adams]

This code is actually not correct. If a string is presented which has it's first word greater than the maximum length, it will only return ellipsis.

A correct one which accounts for this edge case is:

export function truncateString(str: string, maxLength: number) {
    if (str.length <= maxLength) {
        return str;
    }
    // do we have a space? If not, truncate the word.
    if (str.lastIndexOf(' ') === -1) {
        return str.substr(0, maxLength) + '...';
    }

    if (str.lastIndexOf(' ', maxLength) === -1) {
        return str.substr(0, maxLength) + '...';
    }

    return str.substr(0, str.lastIndexOf(' ', maxLength)) + '...';

}

So one line doesn't cut it here.

[Ben Sinclair]

I'm going to suggest an 80-character limit on "one line" code samples, because otherwise I could minimise the code for Excel and call it a one-liner!

[lionel-rowe]

I guess a reasonable interpretation of "one-liners" is anything you can reasonably do without semicolons or newlines.