Add updateLastLog method, prevent exceptions for programmatic calls to log in empty console

Author: snowak-cb

README.md

@@ -67,6 +67,7 @@ Properties you can pass to the console element
 | Member	| Type							| Description
 | ----		| ----							| ----
 | log		| (...messages: any)=>void			| Log messages to the console. If string, print the value, otherwise, print the JSON value of the message.
+| updateLastLog| (...messages: any)=>void			| Replace the last message in the console. Useful for progress indicators.
 | logX		| (type: string, ...messages: any)=>void	| Log messages of a particular type to the console. The messages will be given the class `react-console-message-{type}`.
 | return	| ()=>void					| Signal the current command has finished and a new prompt should be displayed.
 | clearScreen	| ()=>void					| Clear the visible log in the console. Does not clear command history.

src/react-console.tsx

@@ -175,15 +175,32 @@ export default class extends React.Component<ConsoleProps,ConsoleState> {
 		focus?: HTMLElement;
 	} = {};
 	// Command API
+	updateLastLog = (...messages: any[]) => {
+		let log = this.state.log;
+		if(!log.length){
+			log.push({label: '', command: '', message: [] });
+		}
+		let indexToReplace = log[this.state.log.length-1].message.length > 0 ? log[this.state.log.length-1].message.length - 1 : 0;
+		log[this.state.log.length-1].message[indexToReplace] = {value: messages};
+		this.setState({
+			log: log,
+		}, this.scrollIfBottom() );
+	}
 	log = (...messages: any[]) => {
 		let log = this.state.log;
+		if(!log.length){
+			log.push({label: '', command: '', message: [] });
+		}
 		log[this.state.log.length-1].message.push({value: messages});
 		this.setState({
 			log: log,
 		}, this.scrollIfBottom() );
 	}
 	logX = (type: string, ...messages: any[]) => {
 		let log = this.state.log;
+		if(!log.length){
+			log.push({label: '', command: '', message: [] });
+		}
 		log[this.state.log.length-1].message.push({type: type, value: messages});
 		this.setState({
 			log: log,