检查输入是否包含值或其他值

Question

I am stuck on trivial issue, how to simply check if textarea contains "12" OR "34" value? Why does the code attached below does not work?

 function check() { if (V1.value == ('12' || '34')) { alert('Yes'); } else { alert("No"); } }

 <textarea id="V1"></textarea><br> <button onclick="check()">Check</button>

Answer 1

It should be if(V1.value == '12' || V1.value == '34') .

('12' || '34') will simply evaluate to "12" , so your statement is just checking if the value is 12.

 function check() { if(V1.value == '12' || V1.value == '34') { alert('Yes'); } else { alert("No"); } }

 <textarea id="V1"></textarea><br> <button onclick="check()">Check</button>

Answer 2

It should be V1.value === "12" || V1.value === "34" V1.value === "12" || V1.value === "34" .

Also you need to get the #V1 input with:

const V1 = document.getElementById("V1");

 const V1 = document.getElementById("V1"); function check() { if (V1.value === "12" || V1.value === "34") { alert("Yes"); } else { alert("No"); } }

 <textarea id="V1"></textarea> <br /> <button onclick="check()">Check</button>

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This can be done in a much simple way:

 const V1 = document.getElementById("V1"); function check() { if (V1.value === "12" || V1.value === "34") alert("Yes"); else alert("No"); }

 <textarea id="V1"></textarea> <br /> <button onclick="check()">Check</button>

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You can do this in this way also:

 const V1 = document.getElementById("V1"); function check() { V1.value === "12" || V1.value === "34"? alert("Yes"): alert("No") };

 <textarea id="V1"></textarea> <br /> <button onclick="check()">Check</button>