导入的函数在 render() 下不起作用

Question

I am attempting to move a bunch of reusable functions into a convenient place, but I'm having issues with using them in other files. I am using a static React.js frontend without Node.

miscFunctions.js

export const capitalize = (string) => {
  return string.charAt(0).toUpperCase() + string.slice(1);
}

module.exports = {
  capitalize,
  other functions...
}

Test.js

import React, { Component } from 'react';
import capitalize from './miscFunctions';

class Test extends Component {
  constructor(props) {
    super(props);
    this.capitalize = capitalize.bind(this);
  }
  render() {
    return (
      <div>
        {this.capitalize("foo")}
      </div>
    );
  }
}

export default Test;

capitalize() works just fine so long as it's used in a class function, but once I try to use it within render(), it doesn't exist. I get the message "TypeError: Cannot read property 'bind' of undefined"

Answer 1

You don't need to put the capitalize function on the component at all. You can remove it from the constructor and just use it as is.

capitalize is a named export, so you need to import it with that in mind.

// miscFunctions.js
export const capitalize = (string) => {
  return string.charAt(0).toUpperCase() + string.slice(1);
}

// Test.js
import React, { Component } from 'react';
import { capitalize } from './miscFunctions';

class Test extends Component {
  render() {
    return (
      <div>
        {capitalize("foo")}
      </div>
    );
  }
}

export default Test;