cost of conditional function call

perf.js

var microtime = require('microtime'),
    i, iterations = 1000000,
    t0, t1, base,
    runFoo,
    whatever = 1000000000000000,
    obj = {
        foo: function () {
            whatever += 1;
        },
        run: function () {
            whatever += 1;
        }
    };


function report(time, name) {
    //console.log(time + '\t+' + Math.round(100*(time-base)/base) + '%\t' + name);
    console.log(time + '\t' + Math.round(100*time/base) + '%\t' + name);
}
function switchFoo(bool) {
    runFoo = bool;
}


// baseline
t0 = microtime.now();
for (i = 0; i < iterations; i += 1) {
    obj.run();
}
t1 = microtime.now();
base = t1 - t0;
console.log('-------------------- baseline');
report(base, 'run()');


console.log();
console.log('-------------------- have foo');
switchFoo(true);


t0 = microtime.now();
for (i = 0; i < iterations; i += 1) {
    if (runFoo) obj.foo(i);
    obj.run();
}
t1 = microtime.now();
report(t1 - t0, 'if bool, foo()');


t0 = microtime.now();
for (i = 0; i < iterations; i += 1) {
    if (obj.foo) obj.foo(i);
    obj.run();
}
t1 = microtime.now();
report(t1 - t0, 'if foo, foo()');


t0 = microtime.now();
for (i = 0; i < iterations; i += 1) {
    runFoo && obj.foo(i);
    obj.run();
}
t1 = microtime.now();
report(t1 - t0, 'bool && foo()');


t0 = microtime.now();
for (i = 0; i < iterations; i += 1) {
    obj.foo && obj.foo(i);
    obj.run();
}
t1 = microtime.now();
report(t1 - t0, 'foo && foo()');


console.log();
console.log('-------------------- no foo');
switchFoo(false);
delete obj.foo;


t0 = microtime.now();
for (i = 0; i < iterations; i += 1) {
    if (runFoo) obj.foo(i);
    obj.run();
}
t1 = microtime.now();
report(t1 - t0, 'if bool, foo()');


t0 = microtime.now();
for (i = 0; i < iterations; i += 1) {
    if (obj.foo) obj.foo(i);
    obj.run();
}
t1 = microtime.now();
report(t1 - t0, 'if foo, foo()');


t0 = microtime.now();
for (i = 0; i < iterations; i += 1) {
    runFoo && obj.foo(i);
    obj.run();
}
t1 = microtime.now();
report(t1 - t0, 'bool && foo()');


t0 = microtime.now();
for (i = 0; i < iterations; i += 1) {
    obj.foo && obj.foo(i);
    obj.run();
}
t1 = microtime.now();
report(t1 - t0, 'foo && foo()');


console.log();
console.log('-------------------- no-op foo');
obj.foo = function() {};


t0 = microtime.now();
for (i = 0; i < iterations; i += 1) {
    if (obj.foo) obj.foo(i);
    obj.run();
}
t1 = microtime.now();
report(t1 - t0, 'if foo, foo()');


runFoo = true;
t0 = microtime.now();
for (i = 0; i < iterations; i += 1) {
    obj.foo && obj.foo(i);
    obj.run();
}
t1 = microtime.now();
report(t1 - t0, 'foo && foo()');


console.log()
console.log('-------------------- misc');


obj._run = obj.run;
obj.run = function () {
    this._run();
};
t0 = microtime.now();
for (i = 0; i < iterations; i += 1) {
    obj.run();
}
t1 = microtime.now();
report(t1 - t0, 'wrapped run()');
console.log('whatever =', whatever);