JavaScript final

Author: cdmain

javascript/script.js

@@ -0,0 +1,109 @@
+let buffer = '0'
+let runningTotal = 0
+let previousOperator = null
+
+const screen = document.querySelector('.screen')
+
+function buttonClick (value) {
+    if (isNaN(parseInt(value)))
+        handleSymbol(value)
+    else
+        handleNumber(value)
+
+    rerender()
+}
+
+function handleNumber (number) {
+    if (buffer === '0')
+        buffer = number
+    else
+        buffer += number
+}
+
+function handleSymbol (symbol) {
+    switch (symbol) {
+        case 'C' :
+            handleClear()
+            break
+        case '=' :
+            handleEquals()
+            break
+        case '←' :
+            handleBackspace()
+            break
+        case '+' :
+        case '-' :
+        case '÷' :
+        case '×' :
+            handleMath(symbol)
+            break
+    }
+}
+
+function handleClear() {
+    buffer = '0'
+}
+
+function handleEquals() {
+    if (previousOperator === null)
+        return // do nothing
+
+    flushOperation(parseInt(buffer))
+    previousOperator = null
+
+    buffer = "" + runningTotal // maintain buffer as type string
+    runningTotal = 0
+}
+
+function handleBackspace() {
+    if (buffer.length === 1)
+        buffer = '0'
+    else
+        buffer = buffer.substring(0, buffer.length - 1)
+}
+
+function handleMath(mathSymbol) {
+    if (buffer === '0')
+        return // do nothing
+
+    const intBuffer = parseInt(buffer)
+    
+    if (runningTotal === 0) 
+        runningTotal = intBuffer 
+    else
+        flushOperation(intBuffer)
+
+    previousOperator = mathSymbol
+    buffer = '0'
+}
+
+function flushOperation (intBuffer) {
+    switch (previousOperator) {
+        case '+' :
+            runningTotal += intBuffer
+            break
+        case '-' :
+            runningTotal -= intBuffer
+            break
+        case '÷' :
+            runningTotal /= intBuffer
+            break
+        case '×' :
+            runningTotal *= intBuffer
+            break
+    }
+}
+
+function init () {
+    document.querySelector('.calc-buttons')
+        .addEventListener("click", function(event){
+            buttonClick(event.target.innerText)
+        })
+}
+
+function rerender () {
+    screen.innerText = buffer
+}
+
+init()
+