16-FormValidation.md

Lab 16: Form Validation

Objectives

• Add Form Validation

Steps

Add Form Validation

1. Open the file src\project\ProjectForm.js

2. Initialize an errors object as a state variable to {name: '', description: '', budget: ''} so we can hold form errors in the component's state.

   src\projects\ProjectForm.js

   ...
   
   function ProjectForm({
     project: initialProject,
     onSave,
     onCancel,
   }) {
     const [project, setProject] = useState(initialProject);
   + const [errors, setErrors] = useState({
   +   name: '',
   +   description: '',
   +   budget: '',
   + });
   
   ...
   
   }
   ...
   export default ProjectForm;

3. Implement a validate function in the ProjectForm component that meets these requirements.

   1. Name is required.
   2. Name needs to be at least 3 characters long.
   3. Description is required.
   4. Budget must be greater than $0.

   Also, implement an isValid function in the ProjectForm component that checks whether there are any validation errors.

   src\projects\ProjectForm.js

   ...
   function ProjectForm({
     project: initialProject,
     onSave,
     onCancel,
   }) {
     const [project, setProject] = useState(initialProject);
     const [errors, setErrors] = useState({
       name: '',
       description: '',
       budget: '',
     });
   
     const handleChange = (event) => {
       ...
     };
   
   +  function validate(project) {
   +    let errors = { name: '', description: '', budget: '' };
   +    if (project.name.length === 0) {
   +      errors.name = 'Name is required';
   +    }
   +    if (project.name.length > 0 && project.name.length < 3) {
   +      errors.name = 'Name needs to be at least 3 characters.';
   +    }
   +    if (project.description.length === 0) {
   +      errors.description = 'Description is required.';
   +    }
   +    if (project.budget === 0) {
   +      errors.budget = 'Budget must be more than $0.';
   +    }
   +    return errors;
   +  }
   
   +  function isValid() {
   +    return (
   +      errors.name.length === 0 &&
   +      errors.description.length === 0 &&
   +      errors.budget.length === 0
   +    );
   +  }
   
     return (
       ...
     );
   }
   ...
   export default ProjectForm;

4. Call the validate function inside handleChange to determine if there are any errors and then set them into the errors state variable.

   ...
   function ProjectForm({
     project: initialProject,
     onSave,
     onCancel,
   }) {
   ...
   
     const handleChange = (event) => {
       const { type, name, value, checked } = event.target;
       // if input type is checkbox use checked
       // otherwise it's type is text, number etc. so use value
       let updatedValue = type === 'checkbox' ? checked : value;
   
       //if input type is number convert the updatedValue string to a number
       if (type === 'number') {
         updatedValue = Number(updatedValue);
       }
       const change = {
         [name]: updatedValue,
       };
   
       let updatedProject;
       // need to do functional update b/c
       // the new project state is based on the previous project state
       // so we can keep the project properties that aren't being edited like project.id
       // the spread operator (...) is used to
       // spread the previous project properties and the new change
       setProject((p) => {
         updatedProject = new Project({ ...p, ...change });
         return updatedProject;
       });
   +    setErrors(() => validate(updatedProject));
     };
   
   
     return (
       ...
     );
   }
   ...
   export default ProjectForm;

5. Call the isValid function on form submit and return back out of the function before saving changes if the form is invalid.

   src\projects\ProjectForm.js

   ...
   function ProjectForm({
     project: initialProject,
     onSave,
     onCancel,
   }) {
   ...
   
     const handleSubmit = (event) => {
       event.preventDefault();
   +    if (!isValid()) return;
       onSave(project);
     };
   
   ...
   
     return (
       ...
     );
   }
   ...
   export default ProjectForm;

6. In the JSX returned by the component: display the validation messages using the following HTML template.

   <div class="card error">
     <p>error message</p>
   </div>

   src\projects\ProjectForm.js

   ...
   function ProjectForm({
     project: initialProject,
     onSave,
     onCancel,
   }) {
     const [project, setProject] = useState(initialProject);
     const [errors, setErrors] = useState({
       name: '',
       description: '',
       budget: '',
     });
     ...
   
     return (
       <form className="input-group vertical" onSubmit={handleSubmit}>
         <label htmlFor="name">Project Name</label>
         <input
           type="text"
           name="name"
           placeholder="enter name"
           value={project.name}
           onChange={handleChange}
         />
   +      {errors.name.length > 0 && (
   +        <div className="card error">
   +          <p>{errors.name}</p>
   +        </div>
   +      )}
   
         <label htmlFor="description">Project Description</label>
         <textarea
           name="description"
           placeholder="enter description"
           value={project.description}
           onChange={handleChange}
         />
   +      {errors.description.length > 0 && (
   +        <div className="card error">
   +          <p>{errors.description}</p>
   +        </div>
   +      )}
   
         <label htmlFor="budget">Project Budget</label>
         <input
           type="number"
           name="budget"
           placeholder="enter budget"
           value={project.budget}
           onChange={handleChange}
         />
   +      {errors.budget.length > 0 && (
   +        <div className="card error">
   +          <p>{errors.budget}</p>
   +        </div>
   +      )}
   
         <label htmlFor="isActive">Active?</label>
         <input
           type="checkbox"
           name="isActive"
           checked={project.isActive}
           onChange={handleChange}
         />
         <div className="input-group">
           <button className="primary bordered medium">Save</button>
           <span />
           <button type="button" className="bordered medium" onClick={onCancel}>
             cancel
           </button>
         </div>
       </form>
     );
   }
   ...
   export default ProjectForm;

7. Verify the application is working by following these steps.

   1. Click the edit button on any project.
   2. Delete the contents of the project name textbox.
   3. Verify the error message displays.
   4. Test the other validation rules.

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✔ You have completed Lab 16