HowProgrammingWorks
diff --git a/‎JavaScript/5-declarative.js
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+54Lines changed: 54 additions & 0 deletions b/‎JavaScript/5-declarative.js
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+54Lines changed: 54 additions & 0 deletions
@@ -0,0 +1,54 @@
+'use strict';
+
+class LiteralParser {
+  constructor(meta) {
+    this.state = 'start';
+    this.meta = meta;
+  }
+
+  feed(char) {
+    const cases = this.meta[this.state];
+    for (const [key, to] of Object.entries(cases)) {
+      if (key.includes(char)) {
+        if (typeof to === 'string') throw Error(to);
+        to(this, char);
+        return;
+      }
+      if (key === '') throw Error(to);
+    }
+  }
+
+  parse(string) {
+    for (const char of string) this.feed(char);
+    return this.result;
+  }
+}
+
+// Usage
+
+const parser = new LiteralParser({
+  start: {
+    '[': (target) => {
+      target.result = [];
+      target.value = '';
+      target.state = 'value';
+    },
+    '': 'Unexpected character before array',
+  },
+  value: {
+    ' .-0123456789': (target, char) => target.value += char,
+    ',]': (target, char) => {
+      const value = parseFloat(target.value);
+      target.result.push(value);
+      target.value = '';
+      if (char === ']') target.state = 'end';
+    },
+    '': 'Unexpected character in value',
+  },
+  end: {
+    '': 'Unexpected character after array',
+  },
+});
+
+const array = parser.parse('[5, 7.1, -2, 194.5, 32]');
+console.log({ array });