Most JS engines have very fast rope-like implementations of strings in JavaScript. String operations in modern JS engines are very fast and hard to beat in any

Most JS engines have very fast rope-like implementations of strings in JavaScript. String operations in modern JS engines are very fast and hard to beat in any language. Updating the text buffer is fast. Displaying it on the screen is the slow part. Anything touching the DOM is slow. But you can use the 2d Canvas instead, which is fast.