foundations-calculator/script.js at main · top-submissions/foundations-calculator · GitHub

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
// Cache DOM elements
const inputDisplay = document.querySelector(".user-input");
const resultDisplay = document.querySelector(".operation-output");

const numberButtons = {
  0: document.querySelector("#zero"),
  1: document.querySelector("#one"),
  2: document.querySelector("#two"),
  3: document.querySelector("#three"),
  4: document.querySelector("#four"),
  5: document.querySelector("#five"),
  6: document.querySelector("#six"),
  7: document.querySelector("#seven"),
  8: document.querySelector("#eight"),
  9: document.querySelector("#nine")
};

const operatorButtons = {
  "+": document.querySelector("#add"),
  "-": document.querySelector("#subtract"),
  "*": document.querySelector("#multiply"),
  "/": document.querySelector("#divide")
};

const specialButtons = {
  clear: document.querySelector("#all-clear"),
  backspace: document.querySelector("#backspace"),
  negate: document.querySelector("#negate"),
  decimal: document.querySelector("#decimal"),
  calculate: document.querySelector("#calculate")
};

function getLastCharacter(str) {
  return str.charAt(str.length - 1);
}

function isInputFull(str) {
  return str.length > 18;
}

function tokenizeExpression(expr) {
  const { tokens, current } = [...expr].reduce(
    (acc, char) => {
      if (/\d|\./.test(char)) {
        acc.current += char;
      } else if (/[+\-*/]/.test(char)) {
        if (acc.current !== "") {
          acc.tokens.push(acc.current);
          acc.current = "";
        }
        acc.tokens.push(char);
      }
      return acc;
    },
    { tokens: [], current: "" }
  );
  if (current !== "") tokens.push(current);
  return tokens;
}

function computeResult(tokens) {
  const firstPass = [];
  for (let i = 0; i < tokens.length; i++) {
    const token = tokens[i];
    if ((token === '*' || token === '/') && firstPass.length) {
      const prev = parseFloat(firstPass.pop());
      const next = parseFloat(tokens[++i]);
      const calc = token === '*' ? prev * next : prev / next;
      firstPass.push(calc.toString());
    } else {
      firstPass.push(token);
    }
  }
  let result = parseFloat(firstPass[0] || 0);
  for (let i = 1; i < firstPass.length; i += 2) {
    const op = firstPass[i];
    const num = parseFloat(firstPass[i + 1]);
    if (op === '+') result += num;
    if (op === '-') result -= num;
  }
  return result;
}

function updateInput(value) {
  inputDisplay.textContent = value;
}

function updateResult(value) {
  resultDisplay.textContent = value;
}

function handleNumber(digit) {
  const current = inputDisplay.textContent;
  if (!isInputFull(current)) updateInput(current + digit);
}

function handleOperator(symbol) {
  const current = inputDisplay.textContent;
  if (current && !/[+\-*/]/.test(getLastCharacter(current))) {
    updateInput(current + symbol);
  }
}

function handleSpecial(action) {
  let current = inputDisplay.textContent;
  switch (action) {
    case 'clear':
      updateInput('');
      updateResult('');
      break;
    case 'backspace':
      updateInput(current.slice(0, -1));
      break;
    case 'negate':
      if (current.startsWith('-')) updateInput(current.slice(1));
      else if (current) updateInput('-' + current);
      break;
    case 'decimal':
      const segment = current.split(/[+\-*/]/).pop();
      if (!segment.includes('.')) updateInput(current + '.');
      break;
    case 'calculate':
      if (current) {
        const tokens = tokenizeExpression(current);
        const result = computeResult(tokens);
        updateResult(result);
        updateInput('');
      }
      break;
  }
}

Object.keys(numberButtons).forEach(digit => {
  numberButtons[digit].addEventListener('click', () => handleNumber(digit));
});

Object.keys(operatorButtons).forEach(symbol => {
  operatorButtons[symbol].addEventListener('click', () => handleOperator(symbol));
});

Object.keys(specialButtons).forEach(action => {
  specialButtons[action].addEventListener('click', () => handleSpecial(action));
});