index.js

const Benchmark = require('benchmark')
const WARN_RANGE = 5
const suite = new Benchmark.Suite({
    onCycle (event) {
        const bench = event.target
        const prev = this.previous && this.previous[bench.name]
        const pctDelta = prev && (((bench.stats.mean - prev.stats.mean) / prev.stats.mean) * 100)
        let colorDiff = !prev
            ? ''
            : `${pctDelta > 0 ? '+' : ''}${pctDelta.toFixed(2)}% `
        colorDiff = ` (${
        pctDelta >= (WARN_RANGE + bench.stats.rme)
            ? chalk.red(colorDiff)
            : pctDelta <= -(WARN_RANGE + bench.stats.rme)
            ? chalk.green(colorDiff)
            : colorDiff
        }±${bench.stats.rme.toFixed(2)}%)`
        console.log('------------------------------------------------')        
        console.log(`     ${bench.name}`)
        console.log('------------------------------------------------')
        if (bench.error) {
            console.log('Error:', bench.error.message || bench.error)
        } else {
            console.log(`  ${
                bench.hz.toFixed(bench.hz < 100 ? 2 : 0)
            } ops/s @ ~${
                (bench.stats.mean * 1000).toFixed(3)
            }ms/op${colorDiff}`)
            console.log(`  Sampled ${
                bench.stats.sample.length
            } in ${
                bench.times.elapsed.toFixed(2)}s.`)
        }
    },
    onComplete() {
        console.log('finished')
    }
}).add('worstcase replace regex', {
    onStart() {
        this.first = true
        this.longString = "";
        this.worstcase = "";
        // Large = 66,000
        for (var i = 0; i < 66000; i++) {
            this.longString += i % 10;
        }
        for (var i=0; i<66000; i += 14) {
            this.worstcase += '&lt;script&gt;' ;
        } 

        this.re  = /&lt;script&gt;/g;
    },
    fn() {
        this.worstcase.replace(this.re, '<script>')
    }
}).add('replace regex', {
    onStart() {
        this.first = true
        this.longString = "";
        this.worstcase = "";
        // Large = 66,000
        for (var i = 0; i < 66000; i++) {
            this.longString += i % 10;
        }
        for (var i=0; i<66000; i += 14) {
            this.worstcase += '&lt;script&gt;' ;
        } 

        this.re  = /&lt;script&gt;/g;
    },
    fn() {
        this.longString.replace(this.re, '<script>')
    }
}).add('substring', {
    onStart() {
        this.first = true
        this.longString = "";
        this.worstcase = "";
        // Large = 66,000
        for (var i = 0; i < 66000; i++) {
            this.longString += i % 10;
        }
        for (var i=0; i<66000; i += 14) {
            this.worstcase += '&lt;script&gt;' ;
        } 

        this.re  = /&lt;script&gt;/g;
    },
    fn() {
        this.longString.substring(0, this.longString.length - 10)
    }
}).add('slice', {
    onStart() {
        this.first = true
        this.longString = "";
        this.worstcase = "";
        // Large = 66,000
        for (var i = 0; i < 66000; i++) {
            this.longString += i % 10;
        }
        for (var i=0; i<66000; i += 14) {
            this.worstcase += '&lt;script&gt;' ;
        } 

        this.re  = /&lt;script&gt;/g;
    },
    fn() {
        this.longString.slice(0, -10)
    }
}).add('substr', {
    onStart() {
        this.first = true
        this.longString = "";
        this.worstcase = "";
        // Large = 66,000
        for (var i = 0; i < 66000; i++) {
            this.longString += i % 10;
        }
        for (var i=0; i<66000; i += 14) {
            this.worstcase += '&lt;script&gt;' ;
        } 

        this.re  = /&lt;script&gt;/g;
    },
    fn() {
        this.longString.substr(0, this.longString.length - 10)
    }
}).run({async: true})

package.json

{
  "name": "benchmarking-strings",
  "version": "1.0.0",
  "description": "",
  "main": "index.js",
  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1"
  },
  "author": "",
  "license": "MIT",
  "dependencies": {
    "benchmark": "^2.1.4"
  }
}