IsDefined

IsDefined(variable)

if(isDefined("form.myVariable")) 
if(structKeyExists(form,"myVariable"))

<cfscript>
    myarray=["1","4","23","5","54"];
    for(i=1; i <= arrayLen(myarray); i++){
    writeoutput(myarray[i] & "<br>");
    }
    writeOutput(isDefined("myarray"))
</cfscript>

<cfscript>
    // Simple Form Processing with IsDefined
    // Business: Contact form with optional fields
    
    // Sample form submissions
    forms = [
        {
            name: "John Smith",
            email: "john@company.com",
            message: "Interested in your services",
            phone: "555-123-4567",
            company: "Tech Corp"
        },
        {
            name: "Sarah Wilson", 
            email: "sarah@startup.com",
            message: "Quick question about pricing"
            // Missing phone and company
        }
    ];
    
    // Simple form processing function
    function processForm(formData) {
        var result = "Form Processing Result:<br><br>";
        
        // Check required fields
        if (isDefined("formData.name") AND isDefined("formData.email") AND isDefined("formData.message")) {
            result &= "✅ <strong>SUCCESS!</strong><br>";
            result &= "<strong>Name:</strong> " & formData.name & "<br>";
            result &= "<strong>Email:</strong> " & formData.email & "<br>";
            result &= "<strong>Message:</strong> " & formData.message & "<br>";
            
            // Check optional fields safely
            if (isDefined("formData.phone")) {
                result &= "<strong>Phone:</strong> " & formData.phone & "<br>";
            } else {
                result &= "<strong>Phone:</strong> Not provided<br>";
            }
            
            if (isDefined("formData.company")) {
                result &= "<strong>Company:</strong> " & formData.company & "<br>";
            } else {
                result &= "<strong>Company:</strong> Not specified<br>";
            }
            
        } else {
            result &= "❌ <strong>FAILED - Missing required fields</strong><br>";
        }
        
        return result;
    }
</cfscript>

<cfoutput>
    <h1>📝 IsDefined: Form Processing Demo</h1>
    <p><strong>Business Need:</strong> Handle contact forms with optional fields</p>
    <p><strong>Challenge:</strong> Some form fields might be missing</p>
    <p><strong>Solution:</strong> Use isDefined() to check before accessing</p>
    <hr>
    
    <h2>Example 1: Complete Form</h2>
    <div style="background: ##d4edda; padding: 15px; border-radius: 5px;">
        #processForm(forms[1])#
    </div>
    
    <h2>Example 2: Partial Form (Missing Optional Fields)</h2>
    <div style="background: ##d4edda; padding: 15px; border-radius: 5px;">
        #processForm(forms[2])#
    </div>
    
</cfoutput>

<cfscript>
    // Simple URL Parameter Handling with IsDefined
    // Business: Product search with optional filters
    
    // Sample URL parameters (normally from URL scope)
    urlParams = [
        {
            keyword: "laptop"
            // Basic search - no filters
        },
        {
            keyword: "laptop",
            brand: "dell", 
            price: "500-1000",
            rating: "4"
            // Advanced search with filters
        }
    ];
    
    // Simple search function
    function buildSearch(params) {
        var result = "Search Results:<br><br>";
        
        // Check for required keyword
        if (isDefined("params.keyword")) {
            result &= "🔍 <strong>Searching for:</strong> " & params.keyword & "<br>";
            
            var filters = [];
            
            // Check optional filters safely
            if (isDefined("params.brand")) {
                arrayAppend(filters, "Brand: " & params.brand);
            }
            
            if (isDefined("params.price")) {
                arrayAppend(filters, "Price: $" & params.price);
            }
            
            if (isDefined("params.rating")) {
                arrayAppend(filters, "Rating: " & params.rating & "+ stars");
            }
            
            if (arrayLen(filters) > 0) {
                result &= "<strong>Filters:</strong> " & arrayToList(filters, ", ") & "<br>";
            } else {
                result &= "<strong>Filters:</strong> None applied<br>";
            }
            
            result &= "<strong>Status:</strong> ✅ Search ready<br>";
            
        } else {
            result &= "❌ <strong>No search keyword provided</strong><br>";
        }
        
        return result;
    }
</cfscript>

<cfoutput>
    <h1>🔗 IsDefined: URL Parameter Demo</h1>
    <p><strong>Business Need:</strong> Handle product search with optional filters</p>
    <p><strong>Challenge:</strong> URL parameters vary by user and page</p>
    <p><strong>Solution:</strong> Use isDefined() to check what's available</p>
    <hr>
    
    <h2>Example 1: Basic Search (keyword only)</h2>
    <div style="background: ##e3f2fd; padding: 15px; border-radius: 5px;">
        #buildSearch(urlParams[1])#
    </div>
    
    <h2>Example 2: Advanced Search (with filters)</h2>
    <div style="background: ##e3f2fd; padding: 15px; border-radius: 5px;">
        #buildSearch(urlParams[2])#
    </div>
    
</cfoutput>

<cfscript>
    // Simple Configuration Management with IsDefined
    // Business: Handle optional application settings
    
    // Sample configurations
    configs = [
        {
            appName: "My ColdFusion App",
            version: "1.0.0"
            // Basic config - missing optional settings
        },
        {
            appName: "My ColdFusion App", 
            version: "1.0.0",
            debugMode: true,
            emailEnabled: true,
            cacheEnabled: true,
            logLevel: "INFO"
            // Full config with all optional settings
        }
    ];
    
    // Simple configuration loader
    function loadConfig(configData) {
        var result = "Configuration Loaded:<br><br>";
        
        // Load basic required settings
        if (isDefined("configData.appName")) {
            result &= "<strong>App Name:</strong> " & configData.appName & "<br>";
        } else {
            result &= "<strong>App Name:</strong> Default App<br>";
        }
        
        if (isDefined("configData.version")) {
            result &= "<strong>Version:</strong> " & configData.version & "<br>";
        } else {
            result &= "<strong>Version:</strong> 1.0.0<br>";
        }
        
        // Check optional features safely
        if (isDefined("configData.debugMode")) {
            result &= "<strong>Debug Mode:</strong> " & (configData.debugMode ? "Enabled" : "Disabled") & "<br>";
        } else {
            result &= "<strong>Debug Mode:</strong> Disabled (default)<br>";
        }
        
        if (isDefined("configData.emailEnabled")) {
            result &= "<strong>Email Service:</strong> " & (configData.emailEnabled ? "Enabled" : "Disabled") & "<br>";
        } else {
            result &= "<strong>Email Service:</strong> Disabled (default)<br>";
        }
        
        if (isDefined("configData.cacheEnabled")) {
            result &= "<strong>Cache:</strong> " & (configData.cacheEnabled ? "Enabled" : "Disabled") & "<br>";
        } else {
            result &= "<strong>Cache:</strong> Disabled (default)<br>";
        }
        
        if (isDefined("configData.logLevel")) {
            result &= "<strong>Log Level:</strong> " & configData.logLevel & "<br>";
        } else {
            result &= "<strong>Log Level:</strong> ERROR (default)<br>";
        }
        
        result &= "<br>✅ <strong>App started successfully!</strong>";
        
        return result;
    }
</cfscript>

<cfoutput>
    <h1>⚙️ IsDefined: Configuration Demo</h1>
    <p><strong>Business Need:</strong> Handle optional application settings</p>
    <p><strong>Challenge:</strong> Different environments have different config completeness</p>
    <p><strong>Solution:</strong> Use isDefined() with sensible defaults</p>
    <hr>
    
    <h2>Example 1: Basic Configuration</h2>
    <div style="background: ##fff3cd; padding: 15px; border-radius: 5px;">
        #loadConfig(configs[1])#
    </div>
    
    <h2>Example 2: Full Configuration</h2>
    <div style="background: ##d1ecf1; padding: 15px; border-radius: 5px;">
        #loadConfig(configs[2])#
    </div>
    
</cfoutput>