node / javascript performance: string concat operator (+) vs array.join()

11261409.md

Performance Comprison:

Section 1 :

string concatenate operator, for short string but large times.

Section 2 :

array join(), for short string but large times.

node version : v4.1.2 platform: Intel I7, 16G DDR3, Ubuntu x64

start = process.hrtime();
for(let i = 0 ; i < N; i++) {
    string = 'asdfjkl' + i +  '#' + (i * 2) + 'okaneinij';
}
console.log('section 1 : ' + timeUse(start));



var string2;
start = process.hrtime();
for(let i = 0 ; i < N; i++) {
    string2 = ['asdfjkl', i,  '#', (i * 2), 'okaneinij'].join(' ');
}
console.log('section 2 : ' + timeUse(start));

result:

# N : 1K
section 1 : 139679ns
section 2 : 1028747ns

# N : 1M
section 1 : 176692203ns
section 2 : 567614619ns

many string concatenate to one long string.

start = process.hrtime();
for(let i = 0 ; i < N; i++) {
    string += i.toString();
}
console.log('section 1 : ' + timeUse(start));


start = process.hrtime();
for(let i = 0 ; i < N; i++) {
    ary.push(i.toString());
}
ary.join(' ');
console.log('section 2 : ' + timeUse(start));

result :

# N : 10
section 1 : 85186ns
section 2 : 28666ns

# N : 100
section 1 : 120392ns
section 2 : 49320ns

# N : 10K
section 1 : 3127081ns
section 2 : 3803529ns

In the 2nd test, why do you use join(' ') not join('')?