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Add dynamic form validation with phone and SSN checks #5

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8 changes: 8 additions & 0 deletions static/js/form.js
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Original file line number Diff line number Diff line change
Expand Up @@ -35,5 +35,13 @@ function renderForm(fields) {
wrapper.appendChild(label);
wrapper.appendChild(input);
form.appendChild(wrapper);

if (typeof attachValidation === 'function') {
attachValidation(input, field.validation || {});
}
});
const submit = document.createElement('button');
submit.type = 'submit';
submit.textContent = 'Submit';
form.appendChild(submit);
}
76 changes: 76 additions & 0 deletions static/js/validation.js
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Original file line number Diff line number Diff line change
@@ -0,0 +1,76 @@
const fieldErrors = {};

function isValidPhone(value) {
const digits = value.replace(/\D/g, '');
return /^\d{10}$/.test(digits);
}

function isValidSSN(value) {
return /^\d{3}-\d{2}-\d{4}$/.test(value);
}

function withinLength(value, max = 15) {
return value.length <= max;
}

function validateField(input, rules = {}) {
const value = input.value.trim();
const name = input.name;
const errors = [];

if (rules.required && !value) {
errors.push(`${name} is required`);
}

if (value && !withinLength(value)) {
errors.push(`${name} must be at most 15 characters`);
}

if (name.toLowerCase().includes('phone') && value && !isValidPhone(value)) {
errors.push('Phone number must be 10 digits');
}

if (name.toLowerCase().includes('ssn') && value && !isValidSSN(value)) {
errors.push('SSN must match ###-##-####');
}

if (rules.minLength && value.length < rules.minLength) {
errors.push(`${name} must be at least ${rules.minLength} characters`);
}

if (rules.min !== undefined && value !== '' && Number(value) < rules.min) {
errors.push(`${name} must be at least ${rules.min}`);
}

if (rules.max !== undefined && value !== '' && Number(value) > rules.max) {
errors.push(`${name} must be at most ${rules.max}`);
}

if (errors.length) {
fieldErrors[name] = errors;
} else {
delete fieldErrors[name];
}
renderErrors();
}

function renderErrors() {
const container = document.getElementById('error-messages');
if (!container) return;
container.innerHTML = '';
Object.values(fieldErrors).forEach((errs) => {
errs.forEach((err) => {
const p = document.createElement('p');
p.textContent = err;
container.appendChild(p);
});
});
}

function attachValidation(input, rules) {
input.addEventListener('input', () => validateField(input, rules));
input.addEventListener('blur', () => validateField(input, rules));
}

// expose to global scope
window.attachValidation = attachValidation;
2 changes: 2 additions & 0 deletions templates/index.html
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Original file line number Diff line number Diff line change
Expand Up @@ -3,10 +3,12 @@
<head>
<meta charset="UTF-8">
<title>Dynamic Form</title>
<script src="{{ url_for('static', filename='js/validation.js') }}" defer></script>
<script src="{{ url_for('static', filename='js/form.js') }}" defer></script>
</head>
<body>
<h1>Dynamic Form</h1>
<form id="dynamic-form"></form>
<div id="error-messages" style="color: red;"></div>
</body>
</html>