Add .word directive

asm.js

@@ -90,6 +90,7 @@ const State = Object.freeze({
     AT_MEM:       18,
     AT_ADDR:      19,
     BYTE:         20,
+    WORD:         21,
 });
 
 const Action = Object.freeze({
@@ -149,6 +150,7 @@ class Parser {
             ".global": State.GLOBAL_NAME,
             ".at":     State.AT_MEM,
             ".byte":   State.BYTE,
+            ".word":   State.WORD,
         };
         this.handlers = {
             [State.TOP]:          (token) => this.token_top(token),
@@ -172,6 +174,7 @@ class Parser {
             [State.AT_MEM]:       (token) => this.token_at_mem(token),
             [State.AT_ADDR]:      (token) => this.token_at_addr(token),
             [State.BYTE]:         (token) => this.token_byte(token),
+            [State.WORD]:         (token) => this.token_word(token),
         };
 
         this.results = [];
@@ -477,6 +480,25 @@ class Parser {
         return action;
     }
 
+    token_word(token) {
+        if (token == LINE_END) {
+            this.state = State.TOP;
+            return;
+        }
+        const action = { type: Action.DATA, size: 2 };
+        const value = this.integer(token);
+        if (value == null) {
+            console.error(
+                `ERROR: Unexpected token ${token}, expected value`);
+            return;
+        } else {
+            if (value > 0xffff)
+                console.error(`WARNING: Value ${token} is truncated`);
+            action.value = [ value & 0xff, (value >> 8) & 0xff ];
+        }
+        return action;
+    }
+
     mem_action() {
         const action = {
             type: Action.MEM,