纯js 格式化json字符串

╰半橙微兮° 2022-05-10 13:42 253阅读 0赞

var at, // The index of the current character
        ch, // The current character
        escapee = {
            '"':  '"',
            '\\': '\\',
            '/':  '/',
            b:    '\b',
            f:    '\f',
            n:    '\n',
            r:    '\r',
            t:    '\t'
        },
        text,
    
        error = function (m) {
            // Call error when something is wrong.
            throw {
                name:    'SyntaxError',
                message: m,
                at:      at,
                text:    text
            };
        },
        
        next = function (c) {
            // If a c parameter is provided, verify that it matches the current character.
            if (c && c !== ch) {
                error("Expected '" + c + "' instead of '" + ch + "'");
            }
            
            // Get the next character. When there are no more characters,
            // return the empty string.
            
            ch = text.charAt(at);
            at += 1;
            return ch;
        },
        
        number = function () {
            // Parse a number value.
            var number,
                string = '';
            
            if (ch === '-') {
                string = '-';
                next('-');
            }
            while (ch >= '0' && ch <= '9') {
                string += ch;
                next();
            }
            if (ch === '.') {
                string += '.';
                while (next() && ch >= '0' && ch <= '9') {
                    string += ch;
                }
            }
            if (ch === 'e' || ch === 'E') {
                string += ch;
                next();
                if (ch === '-' || ch === '+') {
                    string += ch;
                    next();
                }
                while (ch >= '0' && ch <= '9') {
                    string += ch;
                    next();
                }
            }
            number = +string;
            if (!isFinite(number)) {
                error("Bad number");
            } else {
                return number;
            }
        },
        
        string = function () {
            // Parse a string value.
            var hex,
                i,
                string = '',
                uffff;
            
            // When parsing for string values, we must look for " and \ characters.
            if (ch === '"') {
                while (next()) {
                    if (ch === '"') {
                        next();
                        return string;
                    } else if (ch === '\\') {
                        next();
                        if (ch === 'u') {
                            uffff = 0;
                            for (i = 0; i < 4; i += 1) {
                                hex = parseInt(next(), 16);
                                if (!isFinite(hex)) {
                                    break;
                                }
                                uffff = uffff * 16 + hex;
                            }
                            string += String.fromCharCode(uffff);
                        } else if (typeof escapee[ch] === 'string') {
                            string += escapee[ch];
                        } else {
                            break;
                        }
                    } else {
                        string += ch;
                    }
                }
            }
            error("Bad string");
        },
    
        white = function () {
    
    // Skip whitespace.
    
            while (ch && ch <= ' ') {
                next();
            }
        },
    
        word = function () {
    
    // true, false, or null.
    
            switch (ch) {
            case 't':
                next('t');
                next('r');
                next('u');
                next('e');
                return true;
            case 'f':
                next('f');
                next('a');
                next('l');
                next('s');
                next('e');
                return false;
            case 'n':
                next('n');
                next('u');
                next('l');
                next('l');
                return null;
            }
            error("Unexpected '" + ch + "'");
        },
    
        value,  // Place holder for the value function.
    
        array = function () {
    
    // Parse an array value.
    
            var array = [];
    
            if (ch === '[') {
                next('[');
                white();
                if (ch === ']') {
                    next(']');
                    return array;   // empty array
                }
                while (ch) {
                    array.push(value());
                    white();
                    if (ch === ']') {
                        next(']');
                        return array;
                    }
                    next(',');
                    white();
                }
            }
            error("Bad array");
        },
    
        object = function () {
    
    // Parse an object value.
    
            var key,
                object = {};
    
            if (ch === '{') {
                next('{');
                white();
                if (ch === '}') {
                    next('}');
                    return object;   // empty object
                }
                while (ch) {
                    key = string();
                    white();
                    next(':');
                    if (Object.hasOwnProperty.call(object, key)) {
                        error('Duplicate key "' + key + '"');
                    }
                    object[key] = value();
                    white();
                    if (ch === '}') {
                        next('}');
                        return object;
                    }
                    next(',');
                    white();
                }
            }
            error("Bad object");
        };
    
    value = function () {
    
    // Parse a JSON value. It could be an object, an array, a string, a number,
    // or a word.
    
        white();
        switch (ch) {
        case '{':
            return object();
        case '[':
            return array();
        case '"':
            return string();
        case '-':
            return number();
        default:
            return ch >= '0' && ch <= '9' ? number() : word();
        }
    };
    
    // Return the json_parse function. It will have access to all of the above
    // functions and variables.
    
    module.exports = function (source, reviver) {
        var result;
        
        text = source;
        at = 0;
        ch = ' ';
        result = value();
        white();
        if (ch) {
            error("Syntax error");
        }
    
        // If there is a reviver function, we recursively walk the new structure,
        // passing each name/value pair to the reviver function for possible
        // transformation, starting with a temporary root object that holds the result
        // in an empty key. If there is not a reviver function, we simply return the
        // result.
    
        return typeof reviver === 'function' ? (function walk(holder, key) {
            var k, v, value = holder[key];
            if (value && typeof value === 'object') {
                for (k in value) {
                    if (Object.prototype.hasOwnProperty.call(value, k)) {
                        v = walk(value, k);
                        if (v !== undefined) {
                            value[k] = v;
                        } else {
                            delete value[k];
                        }
                    }
                }
            }
            return reviver.call(holder, key, value);
        }({'': result}, '')) : result;
    };