aa.ja

var i, n = 10000, m = 10;
var a = new Array(m);

var d = +new Date();
i = m; while(i--)
    a[i] = '1';
console.log('fill array', new Date - d);

var d = +new Date();
i = n; while(i--)
    ''.concat.apply('', a);
console.log('concat', new Date - d);

var s, j;
var d = +new Date();
i = n; while(i--)
{
    s = '';
    j = m; while(j--)
        s += '1';
}
console.log('+=', new Date - d);

/*
ff 3.6
fill array 0
concat 143
+= 516

chrome5
fill array 0
concat 169
+= 589

chrome6
fill array 0
concat 178
+= 607

opera 10.60
fill array 0
concat 78
+= 112

ie7
fill array 0
concat 450
+= 460
*/