shift and unshift arr.shift() – extracts an item from the beginning, arr.unshift(...items) – adds items to the beginning. splice: The arr.splice(str) method is a swiss army knife for arrays. It can do everything: insert, remove and replace elements. arr.splice(index[, deleteCount, elem1, ..., elemN]) thisArg: Almost all array methods that call functions – like find, filter, map, with a notable exception of sort, accept an optional additional parameter thisArg. arr.find(func, thisArg); arr.filter(func, thisArg); arr.map(func, thisArg); // ... // thisArg is the optional last argument The value of thisArg parameter becomes this for func. concat: arr.concat(arg1, arg2...) argN: not always an array If an argument argN is an array, then all its elements are copied. Otherwise, the argument itself is copied. Eg: let arr = [1, 2]; alert( arr.concat([3, 4])); // 1,2,3,4 alert( arr.concat([3, 4], [5, 6])); // 1,2,3,4,5,6 alert( arr.concat([3, 4], 5, 6)); // 1,2,3,4,5,6 //one arg is an...
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