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<input type='text' id = 'num1'> + <input type='text' id='num2'> = <input type='text' id='res'> <button onclick='count()'>計(jì)算結(jié)果</button><!-- 點(diǎn)擊按鈕實(shí)現(xiàn)計(jì)算 --> <script> function count(){ if(isNaN(document.getElementById('num1').value) || isNaN(document.getElementById('num2').value)) return alert("請輸入正確的數(shù)字");//判斷輸入數(shù)字是否合法 document.getElementById('res').value = parseFloat(document.getElementById("num1").value) + parseFloat(document.getElementById("num2").value);//將結(jié)果輸出 } </script>