The only way to truly test if a variable is undefined is to do the following. Remember, undefined is an object in Javascript. To determine if a variable or object property exists, It is good to compare to keyword undefined or you can also check the type of the object to string âundefinedâ. In the following JavaScript code we compare the num to the undefined in both way.
Nuclear waste -- The waste from nuclear power plants will be toxic for humans for more than 100,000 years. Itâs untenable now to secure and store all of the waste from the plants that exist. To scale up to 2,500 or 3,000, let alone 17,000 plants is unthinkable.
Answer by TiredSkies. Confidence votes 1.7K. UV radiation is of a high energy, therefore it can cause damage to living cells. The dangers faced by humans include; most commonly damage to the skin, but also damage to the eye and immune system.ltraviolet rays (as all electromagnetic waves with more energy then the visible spectrum) can be dangerous to humans. UV tyically just reacts with the skin to cause burns, th â¦ rough prolonged exposure can cause mutations in the DNA of the skin, which causes skin cancer.