ServiceNow Developer Onboarding Kit

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var ServiceHandlerBase = Class.create();
ServiceHandlerBase.prototype = {

	initialize: function() {
		// Controlled by System Property: 'x_scope.debug.enabled'
		this.debug = gs.getProperty('x_scope.debug.enabled', 'false') == 'true';
		this.logPrefix = '[ServiceHandler]: ';
		this.startTime = new Date().getTime();
	},

	// STANDARD ENTRY POINT
	processLogic: function(payload) {
		var result = this._initResponse();

		try {
			this._logDebug('Starting processLogic with payload: ' + JSON.stringify(payload));

			// 1. Validate Input
			if (!payload) throw new Error('Missing payload parameter.');
			
			// 2. Normalize Data
			var dataObj = (typeof payload === 'string') ? JSON.parse(payload) : payload;
			
			// 3. Execute Business Logic
			// var recordID = this._internalFunction(dataObj);

			// 4. Success Response
			result.status = 'success';
			result.message = 'Operation complete';
			result.data = { processed_at: new GlideDateTime().getDisplayValue() };

		} catch (e) {
			result.status = 'error';
			result.message = e.message;
			this._logError('processLogic failed', e);
		} finally {
			this._logPerformance('processLogic');
		}

		return result;
	},

	// --- HELPERS ---
	
	_initResponse: function() {
		return { status: 'error', message: '', data: null };
	},

	_logDebug: function(msg) {
		if (this.debug) gs.info(this.logPrefix + msg);
	},

	_logError: function(msg, errorObj) {
		var details = (errorObj) ? ' | Msg: ' + errorObj.message + ' | Stack: ' + errorObj.stack : '';
		gs.error(this.logPrefix + 'ERROR: ' + msg + details);
	},

	_logPerformance: function(methodName) {
		if (this.debug) {
			var duration = new Date().getTime() - this.startTime;
			gs.info(this.logPrefix + 'PERF [' + methodName + ']: ' + duration + 'ms');
		}
	},

	type: 'ServiceHandlerBase'
};

📋 Copy Code

function onChange(control, oldValue, newValue, isLoading, isTemplate) {
	if (isLoading || newValue === '') return;

	// UX: Give feedback
	g_form.hideFieldMsg('your_field'); 
	g_form.showFieldMsg('your_field', 'Validating...', 'info');

	// 1. PREPARE PAYLOAD (One JSON object)
	var payload = {
		userID: g_user.userID,
		value: newValue,
		recordID: g_form.getUniqueValue()
	};

	// 2. CALL SERVER
	var ga = new GlideAjax('x_scope.ServiceHandlerBase'); 
	ga.addParam('sysparm_name', 'processLogic');
	ga.addParam('sysparm_data', JSON.stringify(payload)); 

	// 3. HANDLE RESPONSE (Using getXMLAnswer)
	ga.getXMLAnswer(function(answer) {
		g_form.hideFieldMsg('your_field');

		if (!answer) {
			g_form.addErrorMessage('Connection Error: No response from server.');
			return;
		}

		try {
			var response = JSON.parse(answer);

			if (response.status === 'success') {
				// SUCCESS LOGIC
				// g_form.setValue('target', response.data.val);
			} else {
				// LOGIC ERROR (e.g. Validation failed)
				g_form.showFieldMsg('your_field', response.message, 'error');
			}
		} catch (e) {
			// CRITICAL ERROR (HTML response / 500 Error)
			console.error('JSON Parse Error:', e);
			g_form.addErrorMessage('System Error. Please contact support.');
		}
	});
}