Run results for: Concatenation vs substring

Run details:

User agent: Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:87.0) Gecko/20100101 Firefox/87.0

Browser: Firefox 87

Operating system: Ubuntu

Device Platform: Desktop

Date tested: 4 years ago

Test name	Executions per second
Concat	121.3 Ops/sec
Find & Substring	195.2 Ops/sec

Script Preparation code:

var string = "HelloWorld!".repeat(100) + " Hi";

AخA
 
var string = "HelloWorld!".repeat(100) + " Hi";

Tests:

Concat

for (let i = 0; i < 200; ++i) {
  let result = '';
  for (let j = 0; j < string.length; ++j) {
    if (' ' === string[j]) {
      break;
    }
    result += string[j];
  }
}

 
for (let i = 0; i < 200; ++i) {  let result = '';  for (let j = 0; j < string.length; ++j) {    if (' ' === string[j]) {      break;    }    result += string[j];  }}

Find & Substring

for (let i = 0; i < 200; ++i) {
  let j;
  for (j = 0; j < string.length; ++j) {
    if (' ' === string[j]) {
      break;
    }
  }
  let result = string.substring(0, j);
}

 
for (let i = 0; i < 200; ++i) {  let j;  for (j = 0; j < string.length; ++j) {    if (' ' === string[j]) {      break;    }  }  let result = string.substring(0, j);}