TemplateString v2

const ITERATIONS = 100000000;
const RUNS = 100;

const templateStartString = function () {
  const before = new Date().getTime();
  let l = 0;
  for (let i = 0; i < ITERATIONS; i++) {
    l += `${i}def`.length;
  }
  const after = new Date().getTime();
  console.log(l);
  console.log(after-before);
  return after-before;
}

const templateMidString = function () {
  const before = new Date().getTime();
  let l = 0;
  for (let i = 0; i < ITERATIONS; i++) {
    l += `abc${i}def`.length;
  }
  const after = new Date().getTime();
  console.log(l);
  console.log(after-before);
  return after-before;
}

const templateEndString = function () {
  const before = new Date().getTime();
  let l = 0;
  for (let i = 0; i < ITERATIONS; i++) {
    l += `abc${i}`.length;
  }
  const after = new Date().getTime();
  console.log(l);
  console.log(after-before);
  return after-before;
}

const templateDoubleString = function () {
  const before = new Date().getTime();
  let l = 0;
  for (let i = 0; i < ITERATIONS; i++) {
    l += `abc${i}def${i}ghi`.length;
  }
  const after = new Date().getTime();
  console.log(l);
  console.log(after-before);
  return after-before;
}

const templateManyString = function () {
  const before = new Date().getTime();
  let l = 0;
  for (let i = 0; i < ITERATIONS; i++) {
    l += `${i}abc${i}def${i}ghi${i}jkl${i}mno${i}pqr${i}stu${i}vwx${i}yz${i}`.length;
  }
  const after = new Date().getTime();
  console.log(l);
  console.log(after-before);
  return after-before;
}

const concatStartString = function () {
  const before = new Date().getTime();
  let l = 0;
  for (let i = 0; i < ITERATIONS; i++) {
    l += (i + 'def').length;
  }
  const after = new Date().getTime();
  console.log(l);
  console.log(after-before);
  return after-before;
}

const concatMidString = function () {
  const before = new Date().getTime();
  let l = 0;
  for (let i = 0; i < ITERATIONS; i++) {
    l += ('abc' + i + 'def').length;
  }
  const after = new Date().getTime();
  console.log(l);
  console.log(after-before);
  return after-before;
}

const concatEndString = function () {
  const before = new Date().getTime();
  let l = 0;
  for (let i = 0; i < ITERATIONS; i++) {
    l += ('abc' + i).length;
  }
  const after = new Date().getTime();
  console.log(l);
  console.log(after-before);
  return after-before;
}

const concatDoubleString = function () {
  const before = new Date().getTime();
  let l = 0;
  for (let i = 0; i < ITERATIONS; i++) {
    l += ('abc' + i + 'def' + i + 'ghi').length;
  }
  const after = new Date().getTime();
  console.log(l);
  console.log(after-before);
  return after-before;
}

const concatManyString = function () {
  const before = new Date().getTime();
  let l = 0;
  for (let i = 0; i < ITERATIONS; i++) {
    l += (i + 'abc' + i + 'def' + i + 'ghi' + i + 'jkl' + i + 'mno' + i + 'pqr' + i + 'stu' + i + 'vwx' + i + 'yz' + i).length;
  }
  const after = new Date().getTime();
  console.log(l);
  console.log(after-before);
  return after-before;
}

const o = {
  t: {
    start: [],
    mid: [],
    end: [],
    double: [],
    many: []
  },
  c: {
    start: [],
    mid: [],
    end: [],
    double: [],
    many: []
  }
}

// warm up
console.log('start warm up');
concatStartString();
console.log('warm up done');

for (let i = 0; i < RUNS; i++) {
  console.log('RUN ' + ('000' + (i+1)).slice(-3));
  o.t.start.push(templateStartString());
  o.t.mid.push(templateMidString());
  o.t.end.push(templateEndString());
  o.t.double.push(templateDoubleString());
  o.t.many.push(templateManyString());
  o.c.start.push(concatStartString());
  o.c.mid.push(concatMidString());
  o.c.end.push(concatEndString());
  o.c.double.push(concatDoubleString());
  o.c.many.push(concatManyString());
}
const calcs = {
  sum: {
    t: {
      start: 0,
      mid: 0,
      end: 0,
      double: 0,
      many: 0
    },
    c: {
      start: 0,
      mid: 0,
      end: 0,
      double: 0,
      many: 0
    }
  },
  avg: {
    t: {
      start: 0,
      mid: 0,
      end: 0,
      double: 0,
      many: 0
    },
    c: {
      start: 0,
      mid: 0,
      end: 0,
      double: 0,
      many: 0
    }
  },
  sd: {
    t: {
      start: 0,
      mid: 0,
      end: 0,
      double: 0,
      many: 0
    },
    c: {
      start: 0,
      mid: 0,
      end: 0,
      double: 0,
      many: 0
    }
  },
  aad: {
    t: {
      start: 0,
      mid: 0,
      end: 0,
      double: 0,
      many: 0
    },
    c: {
      start: 0,
      mid: 0,
      end: 0,
      double: 0,
      many: 0
    }
  },
  min: {
    t: {
      start: 0,
      mid: 0,
      end: 0,
      double: 0,
      many: 0
    },
    c: {
      start: 0,
      mid: 0,
      end: 0,
      double: 0,
      many: 0
    }
  },
  max: {
    t: {
      start: 0,
      mid: 0,
      end: 0,
      double: 0,
      many: 0
    },
    c: {
      start: 0,
      mid: 0,
      end: 0,
      double: 0,
      many: 0
    }
  },
  median: {
    t: {
      start: 0,
      mid: 0,
      end: 0,
      double: 0,
      many: 0
    },
    c: {
      start: 0,
      mid: 0,
      end: 0,
      double: 0,
      many: 0
    }
  }
}

const calcTemplate = function (name) {
  for (const v of o.t[name]) {
    calcs.sum.t[name] += v;
  }
  calcs.avg.t[name] = calcs.sum.t[name] / RUNS;
  for (const value of o.t[name]) {
    const v = value - calcs.avg.t[name];
    calcs.sd.t[name] += v*v;
    calcs.aad.t[name] += Math.abs(v);
  }
  calcs.sd.t[name] = calcs.sd.t[name] / RUNS;
  calcs.aad.t[name] = calcs.aad.t[name] / RUNS;
  calcs.sd.t[name] = Math.pow(calcs.sd.t[name], 0.5);
  calcs.min.t[name] = Math.min(...o.t[name]);
  calcs.max.t[name] = Math.max(...o.t[name]);
  o.t[name].sort((a,b) => a-b);
  calcs.median.t[name] = (o.t[name][(o.t[name].length - 1) >> 1] + o.t[name][o.t[name].length >> 1]) / 2;
}

const calcConcat = function (name) {
  for (const v of o.c[name]) {
    calcs.sum.c[name] += v;
  }
  calcs.avg.c[name] = calcs.sum.c[name] / RUNS;
  for (const value of o.c[name]) {
    const v = value - calcs.avg.c[name];
    calcs.sd.c[name] += v*v;
    calcs.aad.c[name] += Math.abs(v);
  }
  calcs.sd.c[name] = calcs.sd.c[name] / RUNS;
  calcs.aad.c[name] = calcs.aad.c[name] / RUNS;
  calcs.sd.c[name] = Math.pow(calcs.sd.c[name], 0.5);
  calcs.min.c[name] = Math.min(...o.c[name]);
  calcs.max.c[name] = Math.max(...o.c[name]);
  calcs.median.c[name] = (o.c[name][(o.c[name].length - 1) >> 1] + o.c[name][o.c[name].length >> 1]) / 2;
}

const calc = function () {
  calcTemplate('start');
  calcTemplate('mid');
  calcTemplate('end');
  calcTemplate('double');
  calcTemplate('many');

  calcConcat('start');
  calcConcat('mid');
  calcConcat('end');
  calcConcat('double');
  calcConcat('many');
}

calc();
console.log(JSON.stringify(calcs, null, 2));