var arr = new Map()let prev=""for (let i = 0;i<10000;++i){ prev+="ABC:"; arr.set(+i,prev);} function process(s){ return s.slice(0,s.lastIndexOf(':'))}for (const [key,value] of arr){ arr.delete(key)}var arr = new Map()let prev=[]for (let i = 0;i<10000;++i){ prev =[prev, 'ABC']arr.set(+i,prev);} function process(s){ return s.slice(0,s.length-1)}for (const [key,value] of arr){ arr.delete(key)}var arr = new Map()let prev=[]for (let i = 0;i<10000;++i){ prev = prev.concat('ABC') arr.set(+i,prev);}function process(s){ return s.slice(0,s.length-1)}for (const [key,value] of arr){ arr.delete(key)}console.log("hello")--enable-precise-memory-info flag.
| Test case name | Result |
|---|---|
| String concat | |
| Array spread | |
| Array with concat |
| Test name | Executions per second |
|---|---|
| String concat | 995.2 Ops/sec |
| Array spread | 2.4 Ops/sec |
| Array with concat | 2.0 Ops/sec |
Let's break down the benchmark and explain what is being tested.
Benchmark Definition
The benchmark definition provides a JSON object that describes the experiment. In this case, there is only one benchmark definition:
Individual Test Cases
There are three individual test cases, each with its own Benchmark Definition:
var arr = new Map(); let prev = ""; for (let i = 0; i < 10000; ++i) { prev += "ABC:"; // ... } function process(s) { return s.slice(0, s.lastIndexOf(':')); } // ...
* This test case measures the performance of using `slice()` with a colon (`:`) as the separator. The code creates an array of strings and then deletes each element from the array while keeping track of the previous string.
2. **Test Case 2: Array spread**
* The benchmark definition includes the following JavaScript code:
```javascript
var arr = new Map();
let prev = [];
for (let i = 0; i < 10000; ++i) {
prev = [...prev, 'ABC'];
arr.set(+i, prev);
}
function process(s) {
return s.slice(0, s.length - 1);
}
// ...
* This test case measures the performance of using the spread operator (`...`) to concatenate an array of strings and then deleting each element from the array.
var arr = new Map(); let prev = []; for (let i = 0; i < 10000; ++i) { prev = prev.concat('ABC'); arr.set(+i, prev); } function process(s) { return s.slice(0, s.length - 1); } // ... console.log("hello");
* This test case measures the performance of using `concat()` to concatenate an array of strings and then deleting each element from the array. Note that this code also includes a `console.log` statement before the loop.
**Library Usage**
In all three test cases, the code uses JavaScript's built-in `Map` data structure, which is implemented by the V8 engine used by Google Chrome.
**Special JS Features/Syntax**
There are no special JavaScript features or syntax used in these test cases. The focus is on measuring the performance of different string manipulation techniques using standard JavaScript features.
**Other Considerations**
* **String slicing**: In all three test cases, the code uses `slice()` to extract a substring from the previous string.
* **Array operations**: Each test case measures the performance of different array operations: concatenation and deletion.
* **Performance metrics**: The benchmark reports various performance metrics for each test case, including the number of executions per second.
**Alternatives**
There are several alternatives for measuring string manipulation performance in JavaScript:
1. **String.prototype.repeat()**: This method repeats a string a specified number of times.
2. **Array.prototype.fill()**: This method fills an array with a specified value.
3. **Template literals**: These provide a more efficient way to concatenate strings.
However, these alternatives may not be directly comparable to the original benchmark cases, as they have different performance characteristics and use different techniques for string manipulation.
