<input class="input_text" type="text" placeholder="請輸入上限"
maxlength="4" onkeyup="this.value=this.value.replace(/[^\d\.\d{0,2}]/g,'')" />
0.1~1的正則表達式: /^(0.\d+|0|1)$/
只能輸入整數或小數: /^[0-9]+([.]{1}[0-9]+){0,1}$/