add simple expression parsing

Author: janschoenherr

src/fields.vue

@@ -18,7 +18,7 @@
     import FieldSelect from './components/Select.vue';
     import FieldRange from './components/Range.vue';
     import FieldNumber from './components/Number.vue';
-    import {get, set, each, warn, assign, evaluate, isArray, isString, isUndefined} from './util';
+    import {assign, each, evaluate, get, isArray, isString, isUndefined, set, warn} from './util';
 
     export default {
 
@@ -74,17 +74,13 @@
                 }
             },
 
-            evaluate(expr, values = this.values, config = this.config) {
+            evaluate(expr, values = this.values) {
 
                 if (isString(expr)) {
 
-                    const context = {$match, $values: values};
+                    const context = {$match, $values: values, $get: key => get(values, key)};
 
-                    each(config, ({name = key}, key) =>
-                        set(context, name, get(values, name))
-                    );
-
-                    return evaluate(this, expr, assign(context, values));
+                    return evaluate(this, expr, context);
                 }
 
                 return expr.call(this, values, this);
@@ -133,4 +129,4 @@
         return subject && (new RegExp(pattern, flags).test(subject));
     }
 
-</script>
+</script>

src/util.js

@@ -68,10 +68,19 @@ export function set(obj, key, val) {
     _set(obj, parts.shift(), val);
 }
 
+const quotedStringRe = /([^"']+)((.)(?:[^\3\\]|\\.)*?\3|.)?/g;
+const expressionRe = /((?:\d|true|false|null|undefined|(?:this\.|\$)[\S]+|\W)*)([\w][\w+.]*)?/g;
+const expressions = {};
 export function evaluate(self, expr, context) {
 
+    expressions[expr] = expressions[expr] || expr.replace(quotedStringRe, (match, unquoted, quoted = '') =>
+        unquoted.replace(expressionRe, (match, prefix = '', expr) =>
+            match ? `${prefix}${expr ? `$get('${expr}')` : ''}` : ''
+        ) + quoted
+    );
+
     try {
-        return (Function('c', `with(c){return ${expr}}`)).call(self, context);
+        return (Function('c', `with(c){return ${expressions[expr]}}`)).call(self, context);
     } catch (e) {
         warn(e);
     }