I am trying to make a tool to create MySQL query with javascript. So I have separate input boxes to fill the operator and operands. The example array looks like this.
var array = [ "OR", ["<", "col1", "col2"], [ "AND", ["==", "col3", "col4"], ["!=", "colx", "coly"]]];
var array2 = [ "OR", ["<", "col1", "col2"], [ "AND", ["==", "col3", "col4"], ["!=", "colx", "coly"], ["<", "colo", "othercol"]]];
the expected out put is
"col1 < col2 OR (col3 == col4 AND colx != coly)"
"col1 < col2 OR (col3 == col4 AND colx != coly AND colo < othercol)"
What I am trying is something like this.
function createString(array) {
var string = '';
for(var i = 0; i < array.length; i++) {
if(Array.isArray(array[i])) {
//console.log(array[i]);
if(array[i].length == 3) {
var operator = array[i][0];
var variable1 = array[i][1];
var variable2 = array[i][2];
string+= variable1+operator+variable2;
}else {
//console.log('length is '+array[i].length);
}
//is array
}else {
//string
//console.log('it is string '+ array[i]);
string+=array[i];
}
}
return string;
}
But I don't think I am trying the right algorithm. I am still trying this and I will keep my question updated with each try.
thanks in advance
You can try to convert it using below recursive approach:
const array = [ "OR", ["<", "col1", "col2"], [ "AND", ["==", "col3", "col4"], ["!=", "colx", "coly"]]];
const convert = arg => {
const [operator, operand1, operand2] = arg;
const processOperand = op => Array.isArray(op) ? `(${convert(op)})` : op;
return `${processOperand(operand1)} ${operator} ${processOperand(operand2)}`;
}
console.log(convert(array));EDIT: for your second example you can use below function:
var array2 = [ "OR", ["<", "col1", "col2"], [ "AND", ["==", "col3", "col4"], ["!=", "colx", "coly"], ["<", "colo", "othercol"]]];
const convert = arg => {
const [operator, ...operands] = arg;
const processOperand = op => Array.isArray(op) ? `(${convert(op)})` : op;
return operands.reduce((prev, next) => `${processOperand(prev)} ${operator} ${processOperand(next)}`);
}
console.log(convert(array2));With your current and new examples, you can do like below:
Take out the first element of the array since it will always be an operator.
Do processing recursively on all the elements of the array.
Join all the sub/intermediate results with first operand of the array as the glue.
Don't worry about braces(or you can add one in the join() part below if you like) since AND has a precedence over OR.
var array = [ "OR", ["<", "col1", "col2"], [ "AND", ["==", "col3", "col4"], ["!=", "colx", "coly"], ["<", "colo", "othercol"]]];
function createString(element) {
if(!Array.isArray(element)) return element;
let results = [];
for(let i = 1; i < element.length; ++i){
results.push(createString(element[i]));
}
return results.join(" " + element[0] + " ");
}
console.log(createString(array));