convert a javascript file to only contain singlequotes.

singlequote.js

'use strict';
/*eslint-env node */

var fs = require('fs'),
    esprima = require('esprima');

var input = process.argv[2],
    output = input,
    offset = 0,
    content = fs.readFileSync(input, 'utf-8'),
    tokens = esprima.parse(content, { tokens: true, range: true }).tokens;

function convert(literal) {
    var result = literal.substring(1, literal.length - 1);
    result = result.replace(/'/g, '\'');
    return '\'' + result + '\'';
}

tokens.forEach(function (token) {
    var str;
    if (token.type === 'String' && token.value[0] !== '\'') {
        str = convert(token.value);

        content = content.substring(0, offset + token.range[0]) + str +
            content.substring(offset + token.range[1], content.length);

        offset += (str.length - token.value.length);
    }
});
fs.writeFileSync(output, content);