Obfuscating going wrong - Not same result always

node --version
v10.16.3
"gulp-concat": "~2.3.3",
"gulp-preprocess": "^1.2.0",
"gulp-javascript-obfuscator": "^1.1.2",
The following gulp code is used:

```
var preprocess = require('gulp-preprocess'),
concat = require('gulp-concat'),
javascriptobfuscator = require('gulp-javascript-obfuscator');

gulp.task('app', function() {
return gulp.src('./js/app.js')
.pipe(preprocess({
context: {
HOST: host,
VER: ver
}
}))
.pipe(concat('app.js'))
.pipe(javascriptobfuscator({
reservedStrings:['loadScript','loadCss']
}))
.pipe( gulp.dest('dist/target/js'));
});
```

The following code:
`if(index < scriptFiles.length-1)`

is converted to:
` if (_0x219af0 < _0x441e3a[_0x56ae('0xf')] - 0x1)`

If I step through in Chrome Browser, __0x56ae('0xf')_ is incorrectly equated as '_style_' instead of '_length_'.
If I build it again, it goes fine.
So, it is intermittent. Can somebody point if I am doing anything wrong?

从所示的 gulp 任务开始，重点检查输入 ./js/app.js 和生成的 dist/target/js/app.js，然后反复运行 build，并在 Chrome 中比较混淆后的输出。完成的标准是，重复 build 时始终能正确映射 length 属性，而不是间歇性地产生 style 映射。

由索引模型根据 Issue 内容生成。