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index.js
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index.js
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function isNumberKey(evt)
{
var charCode = (evt.which) ? evt.which : evt.keyCode;
if (charCode != 46 && charCode > 31
&& (charCode < 48 || charCode > 57)
&& (charCode != 43 && charCode != 45 && charCode != 42 && charCode != 47))
return false;
// Check if there's already a period in the input
if (charCode == 46 && document.querySelector('input').value.includes('.'))
return false;
// Check if the last character is an operator
var inputValue = document.querySelector('input').value;
if ((charCode == 43 || charCode == 45 || charCode == 42 || charCode == 47)
&& (inputValue.endsWith('+') || inputValue.endsWith('-') || inputValue.endsWith('*') || inputValue.endsWith('/')))
return false;
return true;
}
function isOperator(value) {
if (value == '÷' || value == 'x' || value == '+' || value == '-') {
return true;
}
return false;
}
function setOperand(operand) {
document.querySelector('input').value += operand;
}
function setOperator(operator) {
switch(operator) {
case 'c':
let input = document.querySelector('input');
input.value = input.value.substring(0, input.value.length - 1);
break;
case '÷':
document.querySelector('input').value += operator;
break;
case 'x':
document.querySelector('input').value += operator;
break;
case '-':
document.querySelector('input').value += operator;
break;
case '+':
document.querySelector('input').value += operator;
break;
case '=':
// if equal =
let inputValue = document.querySelector('input').value;
let operand = '';
let arr = [];
for (let i = 0; i < inputValue.length; i++) {
// for each char in string.
if (isOperator(inputValue[i])) {
if (operand) {
arr.push(operand);
}
arr.push(inputValue[i]); // push the operator
operand = ''; // clear the operand
} else {
// concat the char to form the operands till there's an operator
operand += inputValue[i];
}
}
if (operand) {
arr.push(operand);
}
const result = calculate(arr);
document.querySelector('input').value = `= ${result}`;
break;
}
}
function calculate(array) {
let operator;
return array.reduce((result, val) => {
if(isOperator(val)){
operator = val;
}
else {
switch (operator) {
case '÷':
result /= parseFloat(val);
break;
case 'x':
result *= parseFloat(val);
break;
case '-':
result -= parseFloat(val);
break;
case '+':
result += parseFloat(val);
break;
default:
result = parseFloat(val);
break;
}
}
return result;
}, 0);
}