OK～ 我們在昨天 [Day 11] [Express] 用 Express 和 Node 做一個簡單的 web application 做好了一個只有加法的計算機，今天終於要來到這個章節的最後一關挑戰～

這個章節的挑戰是做一個 BMI 計算機。

以下是比較重要需要照著做的規定：

• Create a new file called bmiCalculator.html inside the Calculator folder from the last challenge
• Add an HTML form, this form will make a post request to our server at the route /bmicalculator. The form will have 2 inputs, weight and height with placeholder text that tell the user what they should type into which text box.
• Add a button which says “Caculate BMI”

之前上 Javascript 已經有練習過 BMI Challenge，所以我直接複製貼上：

/* If my weight is 65Kg and my height is 1.8m, I should be able to call your function like this:

var bmi = bmiCalculator(65, 1.8); 

bmi should equal 20 when it's rounded to the nearest whole number.

*/

function bmiCalculator(weight,height) {

    var number = weight / (height * height);
    console.log(number)

    return number
    
}


var bmi = bmiCalculator(65, 1.8); 
console.log("ANSWER: >>>>>>>> " + Math.round(bmi))

好的～ 再來就是把前端弄好，要有兩個輸入匡，分別是身高、體重，而且要有 placeholder 來提示說要輸入什麼。還有，按鈕要叫「Caculate BMI」。

再來是計算結果，題目要的格式是「Your BMI is n」，所以整個計算邏輯會長這樣：

app.post('/bmiCalculator', function(request, response){
    var height = Number(request.body.height);
    var weight = Number(request.body.weight);
    var result = weight / (height * height);

    response.send('Your BMI is ' + result)
})

喔喔差點忘了，app.get 還沒打好，趕快來補一下：

app.get('/bmiCalculator', function(request, response){
    response.sendFile(__dirname + '/bmiCalculator.html')
}) 

OK，現在來看看直接複製貼上的結果如何 XD

Your BMI is 20.20493048039853485403

小數點後面的位數太多，所以加上 Math.floor()：

Your BMI is 20

太好了～ Express.js with Node.js 章節終於結束！

目前進度：

鐵人賽目標是 9/30 上到課程的第 371 小節，目前在 238 小節結束。