JavaScriptのfloor, trunc, toFixedを使用したサンプル

デベロッパーツールのconsoleでご確認下さい。

Math.trunc = Math.trunc || function(x) {
  return x < 0 ? Math.ceil(x) : Math.floor(x);
};
console.log(Math.floor(12.34)); // => 12
console.log(Math.floor(56.78)); // => 56
console.log(Math.floor(1.5));   // => 1
console.log(Math.floor(-0.12)); // => -1
console.log(Math.floor(-1.49)); // => -2
console.log(Math.floor(-1.5));  // => -2
console.log('===================');
console.log((12.34).toFixed(0)); // => '12'
console.log((56.78).toFixed(0)); // => '57'
console.log((1.5).toFixed(0));   // => '2'
console.log((-0.12).toFixed(0)); // => '-0'
console.log((-1.49).toFixed(0)); // => '-1'
console.log((-1.5).toFixed(0));  // => '-2'
console.log('===================');
console.log(Math.trunc(12.34)); // => 12
console.log(Math.trunc(56.78)); // => 56
console.log(Math.trunc(1.5));   // => 1
console.log(Math.trunc(-0.12)); // => -0
console.log(Math.trunc(-1.49)); // => -1
console.log(Math.trunc(-1.5));  // => -1