case_test.js

gistfile1.js

function ifs(x) {
  if(x == 0) {
    return 0;
  } else if(x == 1) {
    return 1;
  } else if(x == 2) {
    return 2;
  } else if(x == 3) {
    return 3;
  } else if(x == 4) {
    return 4;
  } else if(x == 5) {
    return 5;
  } else if(x == 6) {
    return 6;
  } else if(x == 7) {
    return 7;
  } else if(x == 8) {
    return 8;
  } else if(x == 9) {
    return 9;
  } else if(x == 10) {
    return 10;
  } else if(x == 11) {
    return 11;
  } else if(x == 12) {
    return 12;
  } else if(x == 13) {
    return 13;
  } else if(x == 14) {
    return 14;
  } else if(x == 15) {
    return 15;
  } else if(x == 16) {
    return 16;
  } else if(x == 17) {
    return 17;
  } else if(x == 18) {
    return 18;
  } else if(x == 19) {
    return 19;
  }
}

function switches(x) {
  switch(x) {
    case 0:
    return 0;
    case 1:
    return 1;
    case 2:
    return 2;
    case 3:
    return 3;
    case 4:
    return 4;
    case 5:
    return 5;
    case 6:
    return 6;
    case 7:
    return 7;
    case 8:
    return 8;
    case 9:
    return 0;
    case 10:
    return 10;
    case 11:
    return 11;
    case 12:
    return 12;
    case 13:
    return 13;
    case 14:
    return 14;
    case 15:
    return 15;
    case 16:
    return 16;
    case 17:
    return 17;
    case 18:
    return 18;
    case 19:
    return 19;
  }
}

var dispatch = [0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19];
function arrays(x) {
  return dispatch[dispatch[x]];
}

// ~200ms
var start = new Date();
for(var i = 0; i < 1e7; i++) {
  ifs(i % 20);
}
console.log((new Date())-start);

// ~198ms
start = new Date();
for(var i = 0; i < 1e7; i++) {
  switches(i % 20);
}
console.log((new Date())-start);

// ~136ms
start = new Date();
for(var i = 0; i < 1e7; i++) {
  arrays(i % 20);
}
console.log((new Date())-start);