Javascript Compare

compare.js

function isObject(v) {
    return typeof v === 'object' && v !== null
}

function compare(a, b, indent) {
    var toplevel = false;
    if (indent === undefined) {
        indent = 0;
        toplevel = true;
    }
    var log = [];

    var tab = (new Array(indent)).fill('-').join('');
    if(Array.isArray(a) && Array.isArray(b)) {
        a.forEach(function(key) {
            if(b.indexOf(key) === -1) {
                log.push(`${tab}Item '${key}' in A but not in B`);
            }
        });
        b.forEach(function(key) {
            if(a.indexOf(key) === -1) {
                log.push(`${tab}Item '${key}' in B but not in A`);
            }
        });
    } else if(isObject(a) && isObject(b)){
        var aKeys = Object.keys(a);
        var bKeys = Object.keys(b);
        aKeys.forEach(function(key) {
            if(bKeys.indexOf(key) === -1) {
                log.push(`${tab}Key '${key}' in A but not in B`);
            }
        });
        bKeys.forEach(function(key) {
            if(aKeys.indexOf(key) === -1) {
                log.push(`${tab}Key '${key}' in B but not in A`);
            }
        });
        aKeys.forEach(function(key) {
            if(bKeys.indexOf(key) !== -1) {
                var childLogs = compare(a[key], b[key], indent + 1);
                if(childLogs.length) {
                    log.push(`${tab}Key '${key}':`);
                    log = log.concat(childLogs);
                }
            }
        });
    } else if (a !== b) {
        log.push(a);
        log.push(b);
    }

    if(toplevel) {
        console.log(log.join("\n"));
    }

    return log;
}