ractive/src/Ractive/prototype/shared/add.js

Next-generation DOM manipulation

import isNumeric from 'utils/isNumeric';

export default function add ( root, keypath, d ) {
	var value;

	if ( typeof keypath !== 'string' || !isNumeric( d ) ) {
		throw new Error( 'Bad arguments' );
	}

	value = +root.get( keypath ) || 0;

	if ( !isNumeric( value ) ) {
		throw new Error( 'Cannot add to a non-numeric value' );
	}

	return root.set( keypath, value + d );
}