Error: Cannot find module 'syntax-parser'

node版本： v8.11.3

步骤：
1. `npm i syntax-parser --save`

2. 代码
```javascript
const { createLexer } = require('syntax-parser');

const myLexer = createLexer([
{
type: 'whitespace',
regexes: [/^(\s+)/],
ignore: true
},
{
type: 'word',
regexes: [/^([a-zA-Z0-9]+)/]
},
{
type: 'operator',
regexes: [
/^(\(|\))/, // '(' ')'.
/^(\+|\-)/ // operators for + -.
]
}
]);
console.log(myLexer('a + b'));
```
3. 结果：
```
module.js:549
throw err;
^

Error: Cannot find module 'syntax-parser'
at Function.Module._resolveFilename (module.js:547:15)
at Function.Module._load (module.js:474:25)
at Module.require (module.js:596:17)
at require (internal/module.js:11:18)
at Object. (~/sqlweb/test.js:2:25)
at Module._compile (module.js:652:30)
at Object.Module._extensions..js (module.js:663:10)
at Module.load (module.js:565:32)
at tryModuleLoad (module.js:505:12)
at Function.Module._load (module.js:497:3)
```