JavaScript-使用数组检查字符串

Question

This piece of code should return hits = ["Heather, "Heather", "Heather"] but it doesn't. I'm not quite sure what I am doing wrong.

var text = ["Heather", "kfdjsalfjdai", "fdjafhjdksafh", "Heather", "Heather", "fjdiafjdoisfhoids"];
var myName = "Heather";
var hits = [];
for(var i = 0; i < text.length; i++) {
    if (text[i] === myName[i]) {
        for(var j = i; j < (myName.length + i); j++); {
            hits.push(text[j]);
        }
    }
}

Answer 1

You can use array filter function:

var hits = text.filter(function (obj) {
  return obj === myName;
});

Snippet

 var text = ["Heather", "kfdjsalfjdai", "fdjafhjdksafh", "Heather", "Heather", "fjdiafjdoisfhoids"]; var myName = "Heather"; var hits = text.filter(function (obj) { return obj === myName; }); console.log(hits); 

Answer 2

Obligatory use this library answer. Here I use lodash:

var text = ["Heather", "kfdjsalfjdai", "fdjafhjdksafh", "Heather", "Heather", "something"],
    myName = "Heather";

var hits = _.filter(text, _.matches([myName]);

Explanation on what's happening because this isn't intuitive at all. _.filter does the same thing as Array.prototype.filter except it's faster. You can run your own tests below to get an idea:

https://jsperf.com/array-filter-vs-lodash-filter-without-bias/2

The explanation I've heard is that traditional array operations implemented by lodash (map, reduce, filter, etc.) don't have to follow the implementation as detailed by the spec.

Anyways, _.filter takes two arguments: a collection (array or object) and function which returns true or false. If true, it'll return the item.

_.matches is a convenience function which returns a function that takes an argument and matches against the contents of the provided collection.

You could write the above another way:

var hits = _.filter(text, function(str) {
  return str === myName
});

In lodash, we create functions all the time that basically executes an equality check. _.matches is just a convenience function to create equality check function.

Answer 3

Check against myName variable.

var text = ["Heather", "kfdjsalfjdai", "fdjafhjdksafh", "Heather", "Heather", 
                                        "fsomething"];
var myName = "Heather";
var hits = [];

for(var i = 0; i < text.length; i++) {
    if (text[i] === myName) {      
            hits.push(text[i]);      
    }
}
console.log(hits);

Here is a working sample

Answer 4

text[i] will never === myName[i] , because text is an array of strings, whereas myName is just one string. So for example, text[1] === "Heather" , whereas myName[1] === "H" . Any index of myName will just return one character.