support all-boolean mode

index.js

@@ -2,10 +2,14 @@ module.exports = function (args, opts) {
     if (!opts) opts = {};
 
     var flags = { bools : {}, strings : {} };
-
-    [].concat(opts['boolean']).filter(Boolean).forEach(function (key) {
-        flags.bools[key] = true;
-    });
+
+    if (typeof opts['boolean'] === 'boolean' && opts['boolean']) {
+      flags.allBools = true;
+    } else {
+      [].concat(opts['boolean']).filter(Boolean).forEach(function (key) {
+          flags.bools[key] = true;
+      });
+    }
 
     var aliases = {};
     Object.keys(opts.alias || {}).forEach(function (key) {
@@ -68,6 +72,7 @@ module.exports = function (args, opts) {
             var next = args[i + 1];
             if (next !== undefined && !/^-/.test(next)
             && !flags.bools[key]
+            && !flags.allBools
             && (aliases[key] ? !flags.bools[aliases[key]] : true)) {
                 setArg(key, next);
                 i++;

readme.markdown

@@ -55,7 +55,9 @@ options can be:
 
 * `opts.string` - a string or array of strings argument names to always treat as
 strings
-* `opts.boolean` - a string or array of strings to always treat as booleans
+* `opts.boolean` - a boolean, string or array of strings to always treat as
+booleans. if `true` will treat all double hyphenated arguments without equal signs
+as boolean (e.g. affects `--foo`, not `-f` or `--foo=bar`)
 * `opts.alias` - an object mapping string names to strings or arrays of string
 argument names to use as aliases
 * `opts.default` - an object mapping string argument names to default values

test/all_bool.js

@@ -0,0 +1,32 @@
+var parse = require('../');
+var test = require('tape');
+
+test('flag boolean true (default all --args to boolean)', function (t) {
+    var argv = parse(['moo', '--honk', 'cow'], {
+        boolean: true
+    });
+
+    t.deepEqual(argv, {
+        honk: true,
+        _: ['moo', 'cow']
+    });
+
+    t.deepEqual(typeof argv.honk, 'boolean');
+    t.end();
+});
+
+test('flag boolean true only affects double hyphen arguments without equals signs', function (t) {
+    var argv = parse(['moo', '--honk', 'cow', '-p', '55', '--tacos=good'], {
+        boolean: true
+    });
+
+    t.deepEqual(argv, {
+        honk: true,
+        tacos: 'good',
+        p: '55',
+        _: ['moo', 'cow']
+    });
+
+    t.deepEqual(typeof argv.honk, 'boolean');
+    t.end();
+});