stringPadding.js

// String.prototype.padStart + String.prototype.padEnd (ES2017)

function stringPadding(str, width, char) {
    const msgs = str.split(' ')
    msgs.forEach((msg) => {
        const wordLength = msg.length
        let totalPadding = width - wordLength

        const padding = {
            start: totalPadding / 2,
            end: totalPadding,
        }

        if (totalPadding % 2 !== 0) {
            const side = ['start', 'end'].find(() => (Math.random() > 0.5))
            totalPadding -= 1
            padding.start = totalPadding / 2
            padding.end = totalPadding
            padding[side] += 1
        }

        console.log(
            msg
                .padStart(padding.start + wordLength, char)
                .padEnd(width, char)
        )
    })
}

// e.g. stringPadding('sam is my hero', 64, ':')
// -->
// ::::::::::::::::::::::::::::::sam:::::::::::::::::::::::::::::::
// :::::::::::::::::::::::::::::::is:::::::::::::::::::::::::::::::
// :::::::::::::::::::::::::::::::my:::::::::::::::::::::::::::::::
// ::::::::::::::::::::::::::::::hero::::::::::::::::::::::::::::::