my simple orm

orm.js

showError = obj => {
    switch(obj.errCode){
        case '1':
            return 'No table specified'
            break
        case '2':
            return 'Main table has no name'
            break
    }
}
checkProperty = obj => {
    if(obj.hasOwnProperty('tables')){
        if(1==2)
        console.log('>>it has tables')
        if(obj.tables.hasOwnProperty('name')){
            if(1==2)
            console.log('>>it has name')
            return true
        }else{
            showError({errCode:'2'})
            return false
        }
    }else{
        showError({errCode:'1'})
        return false;
    }
}
join = obj => {
    if(checkProperty(obj)){
        maincols = obj.tables.cols.map(cols=>{
            return obj.tables.cols.map(col=>{obj.tables.name+'.'+col})
        })
        childcols = obj.tables.leftjoin.map(tbl=>{
            return tbl.glue.map(glue=>{
                return tbl.name+''+glue.child
            })
        })
        console.log(maincols.concat(childcols).join(','))
        console.log("\n")
        maintbl = 'select ' + obj.tables.cols.map(col=>{return obj.tables.name+'.'+col}).join(',') 
        + obj.tables.leftjoin.map(tbl=>{
            return tbl.cols.map(col=>{return tbl.name+'.'+col}).join(',')
        }).join(',')
        + ' from ' + obj.tables.name + ' left outer join ' + obj.tables.leftjoin.map(tbl=>{
            return tbl.name + ' on ' + tbl.glue.map(glue=>{
                return tbl.name+'.'+glue.child+'='+obj.tables.name+'.'+glue.parent
            }).join(',')
        }).join(' left outer join ')
        return maintbl
    }
}
module.exports = {
    join:join
}

ormuser.js

var express = require('express'),
app = express(),port = 2000,
i = require('./js/orm')

console.log(i.join({
    tables:{
        cols:['a','b'],
        'name':'tableA',
        'leftjoin':[
            {
                'cols':[],
                'name':'tableB',
                'glue':[{'parent':'id','child':'id'}]
            }
        ]
    }
}))
console.log(i.join({
    tables:{
        'cols':['c'],
        'name':'tableA',
        'leftjoin':[
            {
                'cols':['a','b'],
                'name':'tableB',
                'glue':[{'parent':'id','child':'id'}]
            },
            {
                'cols':['a','b'],
                'name':'tableC',
                'glue':[{'parent':'id','child':'id'}]
            }
        ]
    }
}))
console.log(i.join({
    tables:{
        'cols':['c'],
        'name':'tableA',
        'leftjoin':[
            {
                'cols':['a','b'],
                'name':'tableB',
                'glue':[{'parent':'id','child':'id'}]
            },
            {
                'cols':['a','b'],
                'name':'tableC',
                'glue':[{'parent':'id','child':'id'}]
            },
            {
                'cols':['a','f'],
                'name':'tableD',
                'glue':[{'parent':'id','child':'id'}]
            }

        ]
    }
}))
app.listen(port,_=>{
    console.log('Work Order Server start at port ',port)
})