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data types & undefined

by Christopher O

JavaScript

console.clear();

const array = [{}, [], null, undefined, "", 3, true, false];

/* array.forEach(element => console.log(element)); */

for (var i = array.length - 1; i >= 0; i--) {
  
  let x;
  if (array[i]){
  	x = 'y';
  }else{
  	x = 'n';
  }
  console.log( i+": "+(typeof array[i])+' / '+x );
  
  if(typeof array[i] != 'undefined'){
  	console.log("\t1111 Has value");
  }
/*   if(typeof array[i] != undefined){
    console.log("\t2222 Has value");
  }
  if(typeof array[i] !== undefined){
    console.log("\t3333 Has value");
  } */
  if(typeof array[i] !== 'undefined'){
  	console.log("\t4444 Has value");
  }
  
  
}

let y = {};
if(typeof y != 'undefined'){
  console.log("y Has value 1");
}

if(typeof y.yy != 'undefined'){
  console.log("y Has value 2");
}

if(typeof z != 'undefined'){
  console.log("z Has value 1");
}

if(typeof z != 'undefined'){
  console.log("z Has value 2");
}

/* if(typeof z.zz != 'undefined'){
  console.log("z Has value 3");
} */